Toxicological interactions of silver nanoparticles and non-essential metals in human hepatocarcinoma cell line

α-Ketoglutarate prevents hyperlipidemia-induced fatty liver mitochondrial dysfunction and oxidative stress by activating the AMPK-pgc-1α/Nrf2 pathway

α-Ketoglutarate (AKG), a crucial intermediate in the tricarboxylic acid cycle, has been demonstrated to mitigate hyperlipidemia-induced dyslipidemia and endothelial damage. While hyperlipidemia stands as a major trigger for non-alcoholic fatty liver disease, the protection of AKG on hyperlipidemia-induced hepatic metabolic disorders remains underexplored. This study aims to investigate the potential protective effects and mechanisms of AKG against hepatic lipid metabolic disorders caused by acute hyperlipidemia. Our observations indicate that AKG effectively alleviates hepatic lipid accumulation, mitochondrial dysfunction, and loss of redox homeostasis in P407-induced hyperlipidemia mice, as well as in palmitate-injured HepG2 cells and primary hepatocytes. Mechanistic insights reveal that the preventive effects are mediated by activating the AMPK-PGC-1α/Nrf2 pathway. In conclusion, our findings shed light on the role and mechanism of AKG in ameliorating abnormal lipid metabolic disorders in hyperlipidemia-induced fatty liver, suggesting that AKG, an endogenous mitochondrial nutrient, holds promising potential for addressing hyperlipidemia-induced fatty liver conditions.

Mitochondrial Oxidative Stress Is the General Reason for Apoptosis Induced by Different-Valence Heavy Metals in Cells and Mitochondria

This review analyzes the causes and consequences of apoptosis resulting from oxidative stress that occurs in mitochondria and cells exposed to the toxic effects of different-valence heavy metals (Ag+, Tl+, Hg2+, Cd2+, Pb2+, Al3+, Ga3+, In3+, As3+, Sb3+, Cr6+, and U6+). The problems of the relationship between the integration of these toxic metals into molecular mechanisms with the subsequent development of pathophysiological processes and the appearance of diseases caused by the accumulation of these metals in the body are also addressed in this review. Such apoptosis is characterized by a reduction in cell viability, the activation of caspase-3 and caspase-9, the expression of pro-apoptotic genes (Bax and Bcl-2), and the activation of protein kinases (ERK, JNK, p53, and p38) by mitogens. Moreover, the oxidative stress manifests as the mitochondrial permeability transition pore (MPTP) opening, mitochondrial swelling, an increase in the production of reactive oxygen species (ROS) and H2O2, lipid peroxidation, cytochrome c release, a decline in the inner mitochondrial membrane potential (ΔΨmito), a decrease in ATP synthesis, and reduced glutathione and oxygen consumption as well as cytoplasm and matrix calcium overload due to Ca2+ release from the endoplasmic reticulum (ER). The apoptosis and respiratory dysfunction induced by these metals are discussed regarding their interaction with cellular and mitochondrial thiol groups and Fe2+ metabolism disturbance. Similarities and differences in the toxic effects of Tl+ from those of other heavy metals under review are discussed. Similarities may be due to the increase in the cytoplasmic calcium concentration induced by Tl+ and these metals. One difference discussed is the failure to decrease Tl+ toxicity through metallothionein-dependent mechanisms. Another difference could be the decrease in reduced glutathione in the matrix due to the reversible oxidation of Tl+ to Tl3+ near the centers of ROS generation in the respiratory chain. The latter may explain why thallium toxicity to humans turned out to be higher than the toxicity of mercury, lead, cadmium, copper, and zinc.

Antioxidant Supplementation Alleviates Mercury-Induced Cytotoxicity and Restores the Implantation-Related Functions of Primary Human Endometrial Cells

Mercury (Hg) cytotoxicity, which is largely mediated through oxidative stress (OS), can be relieved with antioxidants. Thus, we aimed to study the effects of Hg alone or in combination with 5 nM N-Acetyl-L-cysteine (NAC) on the primary endometrial cells' viability and function. Primary human endometrial epithelial cells (hEnEC) and stromal cells (hEnSC) were isolated from 44 endometrial biopsies obtained from healthy donors. The viability of treated endometrial and JEG-3 trophoblast cells was evaluated via tetrazolium salt metabolism. Cell death and DNA integrity were quantified following annexin V and TUNEL staining, while the reactive oxygen species (ROS) levels were quantified following DCFDA staining. Decidualization was assessed through secreted prolactin and the insulin-like growth factor-binding protein 1 (IGFBP1) in cultured media. JEG-3 spheroids were co-cultured with the hEnEC and decidual hEnSC to assess trophoblast adhesion and outgrowth on the decidual stroma, respectively. Hg compromised cell viability and amplified ROS production in trophoblast and endometrial cells and exacerbated cell death and DNA damage in trophoblast cells, impairing trophoblast adhesion and outgrowth. NAC supplementation significantly restored cell viability, trophoblast adhesion, and outgrowth. As these effects were accompanied by the significant decline in ROS production, our findings originally describe how implantation-related endometrial cell functions are restored in Hg-treated primary human endometrial co-cultures by antioxidant supplementation.

The Role of Silver Nanoparticles in the Diagnosis and Treatment of Cancer: Are There Any Perspectives for the Future?

Cancer is a fatal disease with a complex pathophysiology. Lack of specificity and cytotoxicity, as well as the multidrug resistance of traditional cancer chemotherapy, are the most common limitations that often cause treatment failure. Thus, in recent years, significant efforts have concentrated on the development of a modernistic field called nano-oncology, which provides the possibility of using nanoparticles (NPs) with the aim to detect, target, and treat cancer diseases. In comparison with conventional anticancer strategies, NPs provide a targeted approach, preventing undesirable side effects. What is more, nanoparticle-based drug delivery systems have shown good pharmacokinetics and precise targeting, as well as reduced multidrug resistance. It has been documented that, in cancer cells, NPs promote reactive oxygen species (ROS) production, induce cell cycle arrest and apoptosis, activate ER (endoplasmic reticulum) stress, modulate various signaling pathways, etc. Furthermore, their ability to inhibit tumor growth in vivo has also been documented. In this paper, we have reviewed the role of silver NPs (AgNPs) in cancer nanomedicine, discussing numerous mechanisms by which they render anticancer properties under both in vitro and in vivo conditions, as well as their potential in the diagnosis of cancer.

Biotransformation of graphene oxide within lung fluids could intensify its synergistic biotoxicity effect with cadmium by inhibiting cellular efflux of cadmium

Graphene oxide (GO) has been widely studied and applied in numerous industrial fields and biomedical fields for its excellent physical and chemical properties. Along with the production and applications of GO persist increasing, the environmental health and safety risk (EHS) of GO has been widely studied. However, previous studies almost focused on the biotoxicity of pristine GO under a relatively high exposure dose, without considering its transformation process within environmental and biological mediums. Meanwhile, its secondary toxicity or synergistic effects have not been taken seriously. Here, two different kinds of artificial lung fluids were adopted to incubate pristine GO to mimic the biotransformation process of GO in the lung fluids. And, we explored that biotransformation within the artificial lung fluids could significantly change the physicochemical properties of GO and could enhance its biotoxicity. To reveal the synergistic effects of GO and toxic metal ions, we uncovered that GO could enhance the intracellular content of metal ions by inhibiting the efflux function of ATP binding cassette (ABC) transporters which are distributed on the cellular membrane, and artificial lung fluids incubation of GO could enhance this synergistic effect. Finally, toxic metal ions induced a series of toxic reactions through oxidative stress response and promoted cell death. Moreover, consistent with the results of in vitro experiments, the lungs of mice exposed to GOs combined with Cd exhibited significant inflammation and oxidative stress compared with Cd treatment alone, and it was more remarkable within the mice which were treated with bio-transformed GOs. In summary, this study explored the impact and mechanism of biotransformation of GO in the lung fluids on the synergistic and secondary effects between GO and metal ions.

In Vitro Hepatotoxic and Neurotoxic Effects of Titanium and Cerium Dioxide Nanoparticles, Arsenic and Mercury Co-Exposure

Considering the increasing emergence of new contaminants, such as nanomaterials, mixing with legacy contaminants, including metal(loid)s, it becomes imperative to understand the toxic profile resulting from these interactions. This work aimed at assessing and comparing the individual and combined hepatotoxic and neurotoxic potential of titanium dioxide nanoparticles (TiO₂NPs 0.75–75 mg/L), cerium oxide nanoparticles (CeO₂NPs 0.075–10 μg/L), arsenic (As 0.01–2.5 mg/L), and mercury (Hg 0.5–100 mg/L) on human hepatoma (HepG2) and neuroblastoma (SH-SY5Y) cells. Viability was assessed through WST-1 (24 h) and clonogenic (7 days) assays and it was affected in a dose-, time- and cell-dependent manner. Higher concentrations caused greater toxicity, while prolonged exposure caused inhibition of cell proliferation, even at low concentrations, for both cell lines. Cell cycle progression, explored by flow cytometry 24 h post-exposure, revealed that TiO₂NPs, As and Hg but not CeO₂NPs, changed the profiles of SH-SY5Y and HepG2 cells in a dose-dependent manner, and that the cell cycle was, overall, more affected by exposure to mixtures. Exposure to binary mixtures revealed either potentiation or antagonistic effects depending on the composition, cell type and time of exposure. These findings prove that joint toxicity of contaminants cannot be disregarded and must be further explored.

Evaluation of the Response of HOS and Saos-2 Osteosarcoma Cell Lines When Exposed to Different Sizes and Concentrations of Silver Nanoparticles

Osteosarcoma is considered to be a highly malignant tumor affecting primarily long bones. It metastasizes widely, primarily to the lungs, resulting in poor survival rates of between 19 and 30%. Standard treatment consists of surgical removal of the affected site, with neoadjuvant and adjuvant chemotherapy commonly used, with the usual side effects and complications. There is a need for new treatments in this area, and silver nanoparticles (AgNPs) are one potential avenue for exploration. AgNPs have been found to possess antitumor and cytotoxic activity in vitro, by demonstrating decreased viability of cancer cells through cell cycle arrest and subsequent apoptosis. Integral to these pathways is tumor protein p53, a tumor suppressor which plays a critical role in maintaining genome stability by regulating cell division, after DNA damage. The purpose of this study was to determine if p53 mediates any difference in the response of the osteosarcoma cells in vitro when different sizes and concentrations of AgNPs are administered. Two cell lines were studied: p53-expressing HOS cells and p53-deficient Saos-2 cells. The results of this study suggest that the presence of protein p53 significantly affects the efficacy of AgNPs on osteosarcoma cells.

Toxicological effects of silver nanoparticles and cadmium chloride in macrophage cell line (RAW 264.7): An in vitro approach

BACKGROUND

Silver nanoparticles (AgNP) are largely used in nanotechnological products, but the real risks for human and environment are still poorly understood if we consider the effects of mixtures of AgNP and environmental contaminants, such as non-essential metals.

METHODS

The aim of the present study was to investigate the cytotoxicity and toxicological interaction of AgNP (1-4 nm, 0.36 and 3.6 μg mL^-1) and cadmium (Cd, 1 and 10 μM) mixtures. The murine macrophage cell line RAW 264.7 was used as a model.

RESULTS

Effects were observed after a few hours (4 h) on reactive oxygen species (ROS) and became more pronounced after 24 h-exposure. Cell death occurred by apoptosis, and loss of cell viability (24 h-exposure) was preceded by increases of ROS levels and DNA repair foci, but not of NO levels. Co-exposure potentiated some effects (decrease of cell viability and increase of ROS and NO levels), indicating toxicological interaction.

CONCLUSION

These effects are important findings that must be better investigated, since the interaction of Cd with AgNP from nanoproducts may impair the function of macrophages and represent a health risk for humans.

Exploring silver nanoparticles for cancer therapy and diagnosis

Nanomaterials have emerged as promising candidates for cancer therapy and diagnosis as they can solve long-term issues such as drug solubility, systemic distribution, tumor acquired resistance, and improve the performance of diagnostic methods. Among inorganic nanomaterials, AgNPs have been extensively studied in the context of cancer treatment and the reported results have raised exciting expectations. In this review, we provide an overview of the recent research on AgNPs antitumoral properties, their application in different cancer treatment modalities, their potential in biosensors development, and also highlight the main challenges and possible strategies to enable its translation to clinical use.

The mechanism of cell death induced by silver nanoparticles is distinct from silver cations

Background

Precisely how silver nanoparticles (AgNPs) kill mammalian cells still is not fully understood. It is not clear if AgNP-induced damage differs from silver cation (Ag⁺), nor is it known how AgNP damage is transmitted from cell membranes, including endosomes, to other organelles. Cells can differ in relative sensitivity to AgNPs or Ag⁺, which adds another layer of complexity to identifying specific mechanisms of action. Therefore, we determined if there were specific effects of AgNPs that differed from Ag⁺ in cells with high or low sensitivity to either toxicant.

Methods

Cells were exposed to intact AgNPs, Ag⁺, or defined mixtures of AgNPs with Ag⁺, and viability was assessed. The level of dissolved Ag⁺ in AgNP suspensions was determined using inductively coupled plasma mass spectrometry. Changes in reactive oxygen species following AgNP or Ag⁺ exposure were quantified, and treatment with catalase, an enzyme that catalyzes the decomposition of H₂O₂ to water and oxygen, was used to determine selectively the contribution of H₂O₂ to AgNP and Ag⁺ induced cell death. Lipid peroxides, formation of 4-hydroxynonenol protein adducts, protein thiol oxidation, protein aggregation, and activation of the integrated stress response after AgNP or Ag⁺ exposure were quantified. Lastly, cell membrane integrity and indications of apoptosis or necrosis in AgNP and Ag⁺ treated cells were examined by flow cytometry.

Results

We identified AgNPs with negligible Ag⁺ contamination. We found that SUM159 cells, which are a triple-negative breast cancer cell line, were more sensitive to AgNP exposure less sensitive to Ag⁺ compared to iMECs, an immortalized, breast epithelial cell line. This indicates that high sensitivity to AgNPs was not predictive of similar sensitivity to Ag⁺. Exposure to AgNPs increased protein thiol oxidation, misfolded proteins, and activation of the integrated stress response in AgNP sensitive SUM159 cells but not in iMEC cells. In contrast, Ag⁺ cause similar damage in Ag⁺ sensitive iMEC cells but not in SUM159 cells. Both Ag⁺ and AgNP exposure increased H₂O₂ levels; however, treatment with catalase rescued cells from Ag⁺ cytotoxicity but not from AgNPs. Instead, our data support a mechanism by which damage from AgNP exposure propagates through cells by generation of lipid peroxides, subsequent lipid peroxide mediated oxidation of proteins, and via generation of 4-hydroxynonenal (4-HNE) protein adducts.

Conclusions

There are distinct differences in the responses of cells to AgNPs and Ag⁺. Specifically, AgNPs drive cell death through lipid peroxidation leading to proteotoxicity and necrotic cell death, whereas Ag⁺ increases H₂O₂, which drives oxidative stress and apoptotic cell death. This work identifies a previously unknown mechanism by which AgNPs kill mammalian cells that is not dependent upon the contribution of Ag⁺ released in extracellular media. Understanding precisely which factors drive the toxicity of AgNPs is essential for biomedical applications such as cancer therapy, and of importance to identifying consequences of unintended exposures.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00430-1.

Antimicrobial Properties of Food Nanopackaging: A New Focus on Foodborne Pathogens

Food products contaminated by foodborne pathogens (bacteria, parasites, and viruses) cause foodborne diseases. Today, great efforts are being allocated to the development of novel and effective agents against food pathogenic microorganisms. These efforts even might have a possible future effect in coronavirus disease 2019 (COVID-19) pandemic. Nanotechnology introduces a novel food packaging technology that creates and uses nanomaterials with novel physiochemical and antimicrobial properties. It could utilize preservatives and antimicrobials to extend the food shelf life within the package. Utilizing the antimicrobial nanomaterials into food packaging compounds typically involves incorporation of antimicrobial inorganic nanoparticles such as metals [Silver (Ag), Copper (Cu), Gold (Au)], and metal oxides [Titanium dioxide (TiO2), Silicon oxide (SiO2), Zinc oxide (ZnO)]. Alternatively, intelligent food packaging has been explored for recognition of spoilage and pathogenic microorganisms. This review paper focused on antimicrobial aspects of nanopackaging and presented an overview of antibacterial properties of inorganic nanoparticles. This article also provides information on food safety during COVID-19 pandemic.

Involvement of ABC transporters in the detoxification of non-substrate nanoparticles in lung and cervical cancer cells

This paper aimed to systemically investigate the role of adenosine triphosphate-binding cassette (ABC transporters) in the detoxification of non-substrate nanoparticles including titanium dioxide (n-TiO₂, 5-10 nm) and gold (AuNPs, 3 nm, 15 nm, and 80 nm, named as Au-3, Au-15 and Au-80) in human lung cancer (A549) and human cervical cancer (HeLa) cells. All these nanoparticles were of larger hydrophilic diameters than the channel sizes of ABC transporters, thus should not be the substrates of membrane proteins. After 24-h treatment, they induced significant cytotoxicity as reflected by the reduction in cell viability and glutathione (GSH) contents, as well as the increase in reactive oxygen species (ROS) level. At median-lethal concentrations (10 mg/L n-TiO₂, 2 mg/L Au-3, 5 mg/L Au-15, and 10 mg/L Au-80 for A549 cells; 20 mg/L n-TiO₂, 2 mg/L Au-3, 5 mg/L Au-15, and 10 mg/L Au-80 for Hela cells), all the nanoparticles significantly induced the gene expressions and activities of ABC transporters including P-glycoprotein (PGP) and multidrug resistance associated protein 1 (MRP1). Addition of transporter inhibitors enhanced the ROS levels produced by nanoparticles, but didn't alter their death-inducing effects and intracellular accumulations. With specific suppressors, transcription factors like nuclear factor-erythroid 2-related factor-2 (NRF2) and pregnane X receptor (PXR) were proved to be important in the induction of ABC transporters by nanoparticles. After all, this paper revealed a damage-dependent modulation of ABC transporters by non-substrate nanoparticles. The up-regulated ABC transporters could help in reducing the oxidative stress produced by nanoparticles. Such information should be useful in assessing the environmental risk of nanoparticles, as well as their interactions with other chemical toxicants or drugs.

Influences of a standardized food matrix and gastrointestinal fluids on the physicochemical properties of titanium dioxide nanoparticles

The fast-growing applications of engineered titanium dioxide nanoparticles (e-TiO2-NPs) in the food and pharmaceutical industry in production, packaging, sensors, nutrient delivery systems, and food additives enhance the possibility of oral exposure. Physicochemical transformations may occur when e-TiO2-NPs are incorporated into a food matrix and pass through the human gastrointestinal tract (GIT), which may redefine the toxic effects of the e-TiO2-NPs. In this study, a standardized food model (SFM) and simulated gastrointestinal fluids have been used to study the fate of e-TiO2-NPs following a three-step digestion model in vitro, and a case study was carried out to assess the toxicity of the digested e-TiO2-NPs using an in vitro cellular model. In the absence and presence of the SFM, the transformations of the tristimulus color coordinates, size, agglomeration state, surface charge and solubility of the e-TiO2-NPs in the salivary, gastric and intestinal digestion fluids were compared with those before digestion. The results demonstrate that the presence of the SFM impacted the physicochemical properties of the e-TiO2-NPs significantly. The SFM stabilized the e-TiO2-NP suspensions and acted as a dispersant during each digestive phase. The e-TiO2-NPs showed differentiated transformations of their physicochemical properties after each step of the digestive process. The pH shifts and variable concentrations of enzymes and salts in gastrointestinal fluids induced the transformations of the physicochemical properties of the e-TiO2-NPs. The transformed e-TiO2-NPs could release titanium ion in the gastrointestinal tract. Also, the cell viability induced by e-TiO2-NPs was found to be strongly affected by the presence of the SFM and simulated human GIT fluids. It can be concluded that the physicochemical transformations of the e-TiO2-NPs that were found when they were incorporated into an SFM and passed through the GIT consequently strongly affected the biological effects of the e-TiO2-NPs, which highlights that the toxicity assessment of ingested NPs should use appropriate standardized food models and take realistic physiological conditions into account.

Elucidating the cellular response of silver nanoparticles as a potential combinatorial agent for cisplatin chemotherapy

BACKGROUND

Combination chemotherapy uses drugs that target different cancer hallmarks, resulting in synergistic or additive toxicity. This strategy enhances therapeutic efficacy as well as minimizes drug resistance and side effects. In this study, we investigated whether silver nanoparticles act as a combinatorial partner to cisplatin. In so doing, we compared post-exposure biological endpoints, intracellular drug accumulation, and changes in the proteome profile of tumoral and normal cell lines.

RESULTS

Combinatorial exposure corresponded to cytotoxicity and oxidative stress in both cell lines, yet was substantially more effective against tumoral cells. Proteome analysis revealed that proteins related to energy metabolism pathways were upregulated in both cell lines, suggesting that combinatorial exposure corresponded to energetic modulation. However, proteins and upstream regulators involved in the cell cycle were downregulated, indicating reduced cell proliferation. The response to oxidative stress was markedly different in both cell lines; downregulation of antioxidant proteins in tumoral cells, yet upregulation of the antioxidant defense system in normal cells. These outcomes may have avoided higher cell death rates in normal cells.

CONCLUSIONS

Taken together, our results indicate that combining silver nanoparticles with cisplatin increases the biological activity of the latter, and the combination warrants further exploration for future therapies.

Susceptibility of HepG2 Cells to Silver Nanoparticles in Combination with other Metal/Metal Oxide Nanoparticles

The fast-growing use of nanomaterials in everyday life raises the question about the safety of their use. Unfortunately, the risks associated with the use of nanoparticles (NPs) have not yet been fully assessed. The majority of studies conducted so far at the molecular and cellular level have focused on a single-type exposure, assuming that NPs act as the only factor. In the natural environment, however, we are likely exposed to a mixture of nanoparticles, whose interactions may modulate their impact on living organisms. This study aimed to evaluate the toxicological effects caused by in vitro exposure of HepG2 cells to AgNPs in combination with AuNPs, CdTe quantum dot (QD) NPs, TiO₂NPs, or SiO₂NPs. The results showed that the toxicity of nanoparticle binary mixtures depended on the type and ratio of NPs used. In general, the toxicity of binary mixtures of NPs was lower than the sum of toxicities of NPs alone (protective effect).

TiO2 nanoparticles potentiated the cytotoxicity, oxidative stress and apoptosis response of cadmium in two different human cells

Widespread application of titanium dioxide nanoparticles (nTiO₂) and ubiquitous cadmium (Cd) pollution may increase their chance of co-existence in the natural environment. Toxicological information on co-exposure of nTiO₂ and Cd in mammalian models is largely lacking. Hence, we studied the combined effects of nTiO₂ and Cd in human liver (HepG2) and breast cancer (MCF-7) cells. We observed that nTiO₂ did not produce toxicity to HepG2 and MCF-7 cells. However, moderate concentration of Cd exposure caused cytotoxicity to both cells. Interestingly, non-cytotoxic concentration of nTiO₂ effectively enhanced the oxidative stress response of Cd indicated by pro-oxidants generation (reactive oxygen species, hydrogen peroxide, and lipid peroxidation) and antioxidants depletion (glutathione level and glutathione reductase, superoxide dismutase, and catalase enzymes). Moreover, nTiO₂ potentiated the Cd-induced apoptosis in both cells suggested by altered expression of p53, bax, and bcl-2 genes along with low mitochondrial membrane potential. Cellular uptake results demonstrated that nTiO₂ facilitates the internalization of Cd into the cells. Overall, this study demonstrated that non-cytotoxic concentration of nTiO₂ enhanced the toxicological potential of Cd in human cells. Therefore, more attention should be paid on the combine effects of nTiO₂ and Cd on human health.

Effects of TiO2, SiO2, Ag and CdTe/CdS quantum dots nanoparticles on toxicity of cadmium towards Chlamydomonas reinhardtii

Nanoparticles (NPs) are inevitably released into the aquatic environment for being widely used and may affect the toxicity of other contaminants already present in the environment, such as trace metals. However, the effects of NPs on the ecotoxicity of cadmium (Cd), a common environmental trace metal pollutant, are not well explored. In this study, effects of four widely used NPs TiO₂ (n-TiO₂), SiO₂ (n-SiO₂), Ag (n-Ag) and CdTe/CdS core/shell quantum dots (QD) on the toxicity of Cd to the freshwater algae Chlamydomonas reinhardtii were assessed respectively. Cd reduced the algae biomass, impaired the photosynthetic activities, and led to intracellular oxidative stress of algae. At non-toxic concentrations, both n-TiO₂ (100 mg L^-1) and n-SiO₂ (400 mg L^-1) attenuated the toxicity of Cd towards the algae for reducing the intracellular Cd contents, and the former was more pronounced. QD (0.5 mg L^-1) increased the toxicity of Cd to algae, but n-Ag (0.2 mg L^-1) had no significant influence on the Cd toxicity to algae. The microscopic observations on the ultrastructure of algae cells presented the same phenomena and n-TiO₂, n-SiO₂ aggregations were clearly observed outside the cell wall. Furthermore, the regulation of NPs to the Cd toxicity towards algae was related to the intracellular nitric oxide (NO), an important signaling molecule, rather than the phototaxis of algae. Above all, this study provided a basic understanding about the difference in joint toxicity of different kinds of NPs and Cd to aquatic organisms.

Co-exposure to silver nanoparticles and cadmium induce metabolic adaptation in HepG2 cells

Although multiple studies have reported the toxicological effects and underlying mechanisms of toxicity of silver nanoparticles (AgNP) in a variety of organisms, the interactions of AgNP with environmental contaminants such as cadmium are poorly understood. We used biochemical assays and mass spectrometry-based proteomics to assess the cellular and molecular effects induced by a co-exposure of HepG2 cells to AgNP and cadmium. Cell viability and energy homeostasis were slightly affected after a 4-h exposure to AgNP, cadmium, or a combination of the two; these endpoints were substantially altered after a 24-h co-exposure to AgNP and cadmium, while exposure to one of the two contaminants led only to minor changes. Proteomics analysis followed the same trend: while a 4-h exposure induced minor protein deregulation, a 24-h exposure to a combination of AgNP and cadmium deregulated 43% of the proteome. The toxicity induced by a combined exposure to AgNP and cadmium involved (1) inactivation of Nrf2, resulting in downregulation of antioxidant defense and proteasome-related proteins, (2) metabolic adaptation and ADP/ATP imbalance, and (3) increased protein synthesis possibly to reestablish homeostasis. The adaptation strategy was not sufficient to restore ADP/ATP homeostasis and to avoid cell death.

A perspective of mitochondrial dysfunction in rats treated with silver and titanium nanoparticles (AgNPs and TiNPs)

Nanotechnology is a growing branch of science that deals with the development of structural features bearing at least one dimension in the nano range. More specifically, nanomaterials are defined as objects with dimensions that range from 1 to 100 nm, which give rise to interesting properties. In particular, silver and titanium nanoparticles (AgNPs and TiNPs, respectively) are known for their biological and biomedical properties and are often used in consumer products such as cosmetics, food additives, kitchen utensils, and toys. This situation has increased environmental and occupational exposure to AgNPs and TiNPs, which has placed demand for the risk assessment of NPs. Indeed, the same properties that make nanomaterials so attractive could also prove deleterious to biological systems. Of particular concern is the effect of NPs on mitochondria because these organelles play an essential role in cellular homeostasis. In this scenario, this work aimed to study how AgNPs and TiNPs interact with the mitochondrial respiration chain and to analyze how this interaction interferes in the bioenergetics and oxidative state of the organelles after sub-chronic exposure. Mitochondria were exposed to the NPs by gavage treatment for 21 days to check whether co-exposure of the organelles to the two types of NPs elicited any mitochondrion-NP interaction. More specifically, male Wistar rats were randomly assigned to four groups. Groups I, II, III, and IV received mineral oil, TiNPs (100 μg/kg/day), AgNPs (100 μg/kg/day), and TiNPs + AgNPs (100 μg/kg/day), respectively, by gavage. The liver was immediately removed, and the mitochondria were isolated and used within 3 h. Exposure of mitochondria to TiNPs + AgNPs lowered the respiratory control ratio, causing an uncoupling effect in the oxidative phosphorylation system. Moreover, both types of NPs induced mitochondrial swelling. Extended exposure of mitochondria to the NPs maintained increased ROS levels and depleted the endogenous antioxidant system. The AgNPs and TiNPs acted synergistically-the intensity of the toxic effect on the mitochondrial redox state was more significant in the presence of both types of NPs. These findings imply that the action of the NPs on mitochondria underlie NP toxicity, so future application of NPs requires special attention.

Responses of human hepatoma HepG2 cells to silver nanoparticles and polycyclic aromatic hydrocarbons

The nanotechnology has revolutionized the global market with silver nanoparticles (AgNP) occupying a prominent position due to their remarkable anti-bacterial properties. However, there is no data about the adverse and toxic effects of associations of AgNP and ubiquitous compounds, such as polycyclic aromatic hydrocarbons (PAH). In the current study, we investigated the responses of HepG2 cells to realistic concentrations of AgNP (0.09, 0.9, and 9 ng ml^-1) and mixture of PAH (30 and 300 ng ml^-1), separately and in association. Cell viability and cytotoxicity (neutral red retention and MTT production assays) and proliferation (crystal violet [CV] assay), xenobiotic efflux transporter activity (rhodamine B accumulation assay), ROS levels (dichlorodihydrofluorescein diacetate assay), and lipid peroxidation (pyrenylphosphine-1-diphenyl assay) were analyzed. There was no decreases of cell viability after exposure to AgNP, PAH and most of AgNP + PAH associations, but increases of cell viability/number (CV assay) occurred. Efflux transporter activity was not affected, with exception of one AgNP + PAH associations, ROS levels increased, but lipid peroxidation decreased. Some toxicological interactions occurred, particularly for the highest concentrations of AgNP and PAH, but there is no evidence that these interactions increased the toxicity of AgNP and PAH.