Uptake of Intact Copper Oxide Nanoparticles Causes Acute Toxicity in Cultured Glial Cells

Copper homeostasis and neurodegenerative diseases

Copper, one of the most prolific transition metals in the body, is required for normal brain physiological activity and allows various functions to work normally through its range of concentrations. Copper homeostasis is meticulously maintained through a complex network of copper-dependent proteins, including copper transporters (CTR1 and CTR2), the two copper ion transporters the Cu -transporting ATPase 1 (ATP7A) and Cu-transporting beta (ATP7B), and the three copper chaperones ATOX1, CCS, and COX17. Disruptions in copper homeostasis can lead to either the deficiency or accumulation of copper in brain tissue. Emerging evidence suggests that abnormal copper metabolism or copper binding to various proteins, including ceruloplasmin and metallothionein, is involved in the pathogenesis of neurodegenerative disorders. However, the exact mechanisms underlying these processes are not known. Copper is a potent oxidant that increases reactive oxygen species production and promotes oxidative stress. Elevated reactive oxygen species levels may further compromise mitochondrial integrity and cause mitochondrial dysfunction. Reactive oxygen species serve as key signaling molecules in copper-induced neuroinflammation, with elevated levels activating several critical inflammatory pathways. Additionally, copper can bind aberrantly to several neuronal proteins, including alpha-synuclein, tau, superoxide dismutase 1, and huntingtin, thereby inducing neurotoxicity and ultimately cell death. This study focuses on the latest literature evaluating the role of copper in neurodegenerative diseases, with a particular focus on copper-containing metalloenzymes and copper-binding proteins in the regulation of copper homeostasis and their involvement in neurodegenerative disease pathogenesis. By synthesizing the current findings on the functions of copper in oxidative stress, neuroinflammation, mitochondrial dysfunction, and protein misfolding, we aim to elucidate the mechanisms by which copper contributes to a wide range of hereditary and neuronal disorders, such as Wilson's disease, Menkes' disease, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, and multiple sclerosis. Potential clinically significant therapeutic targets, including superoxide dismutase 1, D-penicillamine, and 5,7-dichloro-2-[(dimethylamino)methyl]-8-hydroxyquinoline, along with their associated therapeutic agents, are further discussed. Ultimately, we collate evidence that copper homeostasis may function in the underlying etiology of several neurodegenerative diseases and offer novel insights into the potential prevention and treatment of these diseases based on copper homeostasis.

Unveiling the interplay of MAPK/NF-κB/MLKL axis in brain health: Omega-3 as a promising candidates against copper neurotoxicity

Excessive intake of copper (Cu) may lead to increased inflammatory responses in brain, which can cause damage to neurons and glial cells, thereby affecting normal brain function. Omega-3 (ω-3) is a common dietary supplement, particularly rich in DHA in the brain, known for its anti-inflammatory properties and its role in lipid balance regulation and structural maintenance. Here, ω-3 is supplemented to Cu-exposed chickens to assess its neuroprotection in vivo and in vitro. Pathologically, ω-3 significantly alleviated structural and functional abnormalities in brain under excess Cu, including barrier disruption, neuronal shrinkage necroptosis and increased release of inflammatory factors such as IL-1β. The molecular docking analyses unveiled high enrichment values of inflammation and MAPK pathway, with IL-1β gene enrichment the highest value. Mechanistically, DHA stabilized the active site of IL-1β, thereby reducing the activation of NF-κB signal and phosphorylation of MAPK/MLKL cascades, ultimately mitigating Cu-induced inflammatory effects. These mechanisms elucidate the action mode of Cu neurotoxicity from aspect of MAPK/NF-κB/MLKL axis and the promising neuroprotection of ω-3.

Potential Environmental and Health Implications from the Scaled-Up Production and Disposal of Nanomaterials Used in Biosensors

Biosensors often combine biological recognition elements with nanomaterials of varying compositions and dimensions to facilitate or enhance the operating mechanism of the device. While incorporating nanomaterials is beneficial to developing high-performance biosensors, at the stages of scale-up and disposal, it may lead to the unmanaged release of toxic nanomaterials. Here we attempt to foster connections between the domains of biosensors development and human and environmental toxicology to encourage a holistic approach to the development and scale-up of biosensors. We begin by exploring the toxicity of nanomaterials commonly used in biosensor design. From our analysis, we introduce five factors with a role in nanotoxicity that should be considered at the biosensor development stages to better manage toxicity. Finally, we contextualize the discussion by presenting the relevant stages and routes of exposure in the biosensor life cycle. Our review found little consensus on how the factors presented govern nanomaterial toxicity, especially in composite and alloyed nanomaterials. To bridge the current gap in understanding and mitigate the risks of uncontrolled nanomaterial release, we advocate for greater collaboration through a precautionary One Health approach to future development and a movement towards a circular approach to biosensor use and disposal.

Nanopesticides: Physico-chemical characterization by a combination of advanced analytical techniques

The recent application of manufactured nanomaterials (MNMs) in plant protection products (PPPs) enhances stability of the active substance (a.s.), minimizes application losses, reduces the quantities of a.s., increases coverage on leaf surface, improves precise application, etc. Besides offering benefits, there is high concern about the potential risk for human and environment associated with the use of nanopesticides. In this study, a panel of complementary methodologies were used to determine size distribution and chemical identification of four different formulations of nanopesticides. Measurements were performed by dynamic light scattering (DLS), transmission electron microscopy (TEM), asymmetric field flow fractionation-multi angle light scattering (AF4-FFF-MALS), gas/liquid chromatography with mass spectrometry (GC-MS/MS, LC-MS/MS) or diode array detector (HPLC-DAD) and inductively coupled plasma mass spectrometry (ICP-MS). Results indicated average size values in the ranges: 27.4-148.7 nm by DLS; 39.1-82.0 nm by AF4-FFF-MALS; and 42-90 nm by TEM. Linked to these nanosized particles both organic active ingredients and inorganic ones were identified. In addition, the obtained data revealed that all the four PPPs contained more than 50% of particles with number size distribution between 1 and 100 nm and, according to the European Commission definition, they can be defined as nanopesticides.

Protective effect of methylene blue against copper oxide nanoparticle-induced neurobehavioral toxicity

Increasing attention has been paid in the past decade to assessing the toxicological effects of nanoparticles and finding a protectant; thus, the current study aimed to investigate the protective effect of the mitochondria-targeting drug methylene blue (MB) against copper oxide nanoparticle (CuO-NP)-induced neurobehavioral toxicity in rats. For this purpose, twenty rats were allocated to four equal groups (n = 5). The negative control group received distilled water intraperitoneally (IP) and Tween 80 (10 %) orally. The CuO-NP group was given a dose of 100 mg/kg of CuO-NPs, administered orally, and the positive control group was treated with 1 mg/kg MB intraperitoneally (IP). The final group was concurrently exposed to CuO-NPs and MB for 14 consecutive days. At the end of the study, each group was neurobehaviorally blind tested relative to other experimental animals, then brain tissue markers were determined and a histopathological examination was conducted. The results showed that supplementation with CuO-NPs induced neurobehavioral alterations; increased Cu content in the brain; and enhanced lipid peroxidation (malondialdehyde [MDA]), protein peroxidation (protein carbonyl [PC]), and DNA oxidative damage (8-hydroxy-2-deoxyguanosine [8-OH-dG]) compared to other treatments. In addition, a decrease was noted in the mitochondrial dehydrogenases' (aldehyde dehydrogenase 2 [ALDH2], and glutamate dehydrogenase [GDH]) activity in Cu-exposed rats. The histopathological findings revealed shrunken, pyknotic, and hypereosinophic cortical neurons and increased immune positive brown staining of caspase-3 protein, indicating apoptosis. Co-treatment with methylene blue ameliorated the neurotoxic effects of CuO-NPs; therefore, MB evidently had a powerful modulatory effect against the neurotoxicity of nano-Cu oxide via its antioxidant and mitochondrial protection properties.

Iron-Doping of Copper Oxide Nanoparticles Lowers Their Toxic Potential on C6 Glioma Cells

Copper oxide nanoparticles (CuO-NPs) are well known for their cytotoxicity which in part has been attributed to the release of copper ions from CuO-NPs. As iron-doping has been reported to reduce the susceptibility of CuO-NPs to dissolution, we have compared pure CuO-NPs and CuO-NPs that had been doped with 10% iron (CuO-Fe-NPs) for copper release and for their toxic potential on C6 glioma cells. Physicochemical characterization revealed that dimercaptosuccinate (DMSA)-coated CuO-NPs and CuO-Fe-NPs did not differ in their size or zeta potential. However, the redox activity and liberation of copper ions from CuO-Fe-NPs was substantially slower compared to that from CuO-NPs, as demonstrated by cyclic voltammetry and by the photometric quantification of the copper ion-bathocuproine complex, respectively. Exposure of C6 cells to these NPs caused an almost identical cellular copper accumulation and each of the two types of NPs induced ROS production and cell toxicity. However, the time- and concentration-dependent loss in cell viability was more severe for cells that had been treated with CuO-NPs compared to cells exposed to CuO-Fe-NPs. Copper accumulation and toxicity after exposure to either CuO-NPs or CuO-Fe-NPs was prevented in the presence of copper chelators, while neutralization of the lysosomal pH by bafilomycin A1 prevented toxicity without affecting cellular copper accumulation or ROS production. These data demonstrate that iron-doping does not affect cellular accumulation of CuO-NPs and suggests that the intracellular liberation of copper ions from CuO-NPs is slowed by the iron doping, which in turn lowers the cell toxic potential of iron-doped CuO-NPs.

Toxicity and effects of copper oxide nanoparticles on cognitive performances in rats

There is increasing scientific evidences that the physical and chemical properties of manufactured nanoparticles lead to an increase in their bioavailability and toxicity. Among them Copper oxide nanoparticles (CuO-NPs) are widely used in different fields. However their potential adverse effects namely on brain functions are still discussed. Thus, the present study aimed to investigate the subacute oral toxicity and effects of CuO-NPs on cognitive performances in rats. Rats were randomly divided into three groups of 8 animals each, a control group received a dose 9‰ sodium chloride and the other groups received a suspension of CuO-NPs at doses of 250 and 500 mg/kg through oral gavage for 14 consecutive days. Multiple behavioral tests showed that CuO-NPs caused little changes in memory and learning performances as well as the locomotors activity, while the anxiety index increased. Copper NPs exposure increased also the liver and stomach relative weights and altered some blood biochemical parameters.