Comparative proteomic analysis of the molecular responses of mouse macrophages to titanium dioxide and copper oxide nanoparticles unravels some toxic mechanisms for copper oxide nanoparticles in macrophages

Biogenic Silver Nanoparticles for Targeted Cancer Therapy and Enhancing Photodynamic Therapy

Different conventional therapeutic procedures are utilized globally to manage cancer cases, yet the mortality rate in patients with cancer remains considerably high. Developments in the field of nanotechnology have included novel therapeutic strategies to deal with cancer. Biogenic (green) metallic silver nanoparticles (AgNPs) obtained using plant-mediated protocols are attractive to researchers exploring cancer treatment. Biogenic AgNPs present advantages, since they are cost-effective, easy to obtain, energy efficient, and less toxic compared to chemically and physically obtained AgNPs. Also, they present excellent anticancer abilities thanks to their unique sizes, shapes, and optical properties. This review provides recent advancements in exploring biogenic AgNPs as a drug or agent for cancer treatment. Thus, great attention was paid to the anticancer efficacy of biogenic AgNPs, their anticancer mechanisms, their efficacy in cancer photodynamic therapy (PDT), their efficacy in targeted cancer therapy, and their toxicity.

Biogenic green metal nano systems as efficient anti-cancer agents

Metal/metal oxide nano systems (M-NSs) of tunable and manipulative properties are emerging suitable for cancer management via immunity development, early-stage diagnosis, nanotherapeutics, and targeted drug delivery systems. However, noticeable toxicity, off-targeted actions, lacking biocompatibility, and being expensive limit their acceptability. Moreover, involving high energy (top-down routes) and hazardous chemicals (bottom-up chemical routes) is altering human cycle. To manage such challenges, biomass (plants, microbes, animals) and green chemistry-based M-NSs due to scalability, affordability, are cellular, tissue, and organ acceptability are emerging as desired biogenic M-NSs for cancer management with enhanced features. The state-of-art and perspective of green metal/metal oxide nano systems (GM-NSs) as an efficient anti-cancer agent including, imaging, immunity building elements, site-specific drug delivery, and therapeutics developments are highlighted in this review critically. It is expected that this report will serve as guideline for design and develop high-performance GM-NSs for establishing them as next-generation anti-cancer agent capable to manage cancer in personalized manner.

Autophagy and lipid droplets are a defense mechanism against toxic copper oxide nanotubes in the eukaryotic microbial model Tetrahymena thermophila

The widespread use of inorganic nanomaterials of anthropogenic origin has significantly increased in the last decade, being now considered as emerging pollutants. This makes it necessary to carry out studies to further understand their toxicity and interactions with cells. In the present work we analyzed the toxicity of CuO nanotubes (CuONT) in the ciliate Tetrahymena thermophila, a eukaryotic unicellular model with animal biology. CuONT exposure rapidly induced ROS generation in the cell leading to oxidative stress and upregulation of genes encoding antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase), metal-chelating metallothioneins and cytochrome P450 monooxygenases. Comet assays and overexpression of genes involved in DNA repair confirmed oxidative DNA damage in CuONT-treated cells. Remarkably, both electron and fluorescent microscopy revealed numerous lipid droplets and autophagosomes containing CuONT aggregates and damaged mitochondria, indicating activation of macroautophagy, which was further confirmed by a dramatic upregulation of ATG (AuTophaGy related) genes. Treatment with autophagy inhibitors significantly increased CuONT toxicity, evidencing the protective role of autophagy towards CuONT-induced damage. Moreover, increased formation of lipid droplets appears as an additional mechanism of CuONT detoxification. Based on these results, we present a hypothetical scenario summarizing how T. thermophila responds to CuONT toxicity. This study corroborates the use of this ciliate as an excellent eukaryotic microbial model for analyzing the cellular response to stress caused by toxic metal nanoparticles.

Immediate and Sustained Effects of Cobalt and Zinc-Containing Pigments on Macrophages

Pigments are among the oldest nanoparticulate products known to mankind, and their use in tattoos is also very old. Nowadays, 25% of American people aged 18 to 50 are tattooed, which poses the question of the delayed effects of tattoos. In this article, we investigated three cobalt [Pigment Violet 14 (purple color)] or cobalt alloy pigments [Pigment Blue 28 (blue color), Pigment Green 14 (green color)], and one zinc pigment [Pigment White 4 (white color)] which constitute a wide range of colors found in tattoos. These pigments contain microparticles and a significant proportion of submicroparticles or nanoparticles (in either aggregate or free form). Because of the key role of macrophages in the scavenging of particulate materials, we tested the effects of cobalt- and zinc-based pigments on the J774A.1 macrophage cell line. In order to detect delayed effects, we compared two exposure schemes: acute exposure for 24 hours and an exposure for 24 hours followed by a 3-day post-exposure recovery period. The conjunction of these two schemes allowed for the investigation of the delayed or sustained effects of pigments. All pigments induced functional effects on macrophages, most of which were pigment-dependent. For example, Pigment Green 19, Pigment Blue 28, and Pigment White 4 showed a delayed alteration of the phagocytic capacity of cells. Moreover, all the pigments tested induced a slight but significant increase in tumor necrosis factor secretion. This effect, however, was transitory. Conversely, only Pigment Blue 28 induced both a short and sustained increase in interleukin 6 secretion. Results showed that in response to bacterial stimuli (LPS), the secretion of tumor necrosis factor and interleukin 6 declined after exposure to pigments followed by a recovery period. For chemoattractant cytokines (MCP-1 or MIP-1α), delayed effects were observed with a secretion decreased in presence of Pigment Blue 28 and Pigment violet 14, both with or without LPS stimuli. The pigments also induced persisting changes in some important macrophage membrane markers such as CD11b, an integrin contributing to cell adhesion and immunological tolerance. In conclusion, the pigments induced functional disorders in macrophages, which, in some cases, persist long after exposure, even at non-toxic doses.

Behavior and toxicity assessment of copper nanoparticles in aquatic environment: A case study on red swamp crayfish

With the wide use of copper nanoparticles (CuNPs) in various industrial and commercial applications, they inevitably enter the aquatic environment. However, their behavior in the aquatic environment and potential toxicity to aquatic organisms remain little known. In this study, we investigated the behavior of CuNPs in freshwater, as well as the toxicity and bioaccumulation of CuNPs and copper sulfate (CuSO₄), used as a positive control for copper ions toxicity, in red swamp crayfish (Procambarus clarkii). The results showed that CuNPs released copper ions into freshwater and aggregated rapidly in freshwater, and their release of copper ions and aggregation slowed down at a higher concentration of CuNPs. The calculated 72-h LC₅₀ values for crayfish were 1.18 and 0.54 mg/L for CuNPs and CuSO₄, respectively. Cu accumulation in the gill and hepatopancreas from CuSO₄ treatments was significantly higher than that from CuNPs, and the highest Cu bioaccumulation level in crayfish was found in the gill, followed by hepatopancreas and muscle with the exposure of copper. The activities of the antioxidative enzymes in the crayfish significantly decreased after exposure to CuNPs for 48 h, compared to the control (without CuNPs or CuSO₄). Histological examination revealed that there was no significant alteration of hepatopancreas in the crayfish exposed to CuNPs. Meanwhile, the growth of crayfish was not significantly inhibited by CuNPs. These results suggested that CuNPs exposure can induce oxidative stress in the crayfish, gill is the main tissue for their accumulation, and their toxicity is mainly caused by the released copper ions.

Repeated Exposure of Macrophages to Synthetic Amorphous Silica Induces Adaptive Proteome Changes and a Moderate Cell Activation

Synthetic amorphous silica (SAS) is a nanomaterial used in a wide variety of applications, including the use as a food additive. Two types of SAS are commonly employed as a powder additive, precipitated silica and fumed silica. Numerous studies have investigated the effects of synthetic amorphous silica on mammalian cells. However, most of them have used an exposure scheme based on a single dose of SAS. In this study, we have used instead a repeated 10-day exposure scheme in an effort to better simulate the occupational exposure encountered in daily life by consumers and workers. As a biological model, we have used the murine macrophage cell line J774A.1, as macrophages are very important innate immune cells in the response to particulate materials. In order to obtain a better appraisal of the macrophage responses to this repeated exposure to SAS, we have used proteomics as a wide-scale approach. Furthermore, some of the biological pathways detected as modulated by the exposure to SAS by the proteomic experiments have been validated through targeted experiments. Overall, proteomics showed that precipitated SAS induced a more important macrophage response than fumed SAS at equal dose. Nevertheless, validation experiments showed that most of the responses detected by proteomics are indeed adaptive, as the cellular homeostasis appeared to be maintained at the end of the exposure. For example, the intracellular glutathione levels or the mitochondrial transmembrane potential at the end of the 10 days exposure were similar for SAS-exposed cells and for unexposed cells. Similarly, no gross lysosomal damage was observed after repeated exposure to SAS. Nevertheless, important functions of macrophages such as phagocytosis, TNFα, and interleukin-6 secretion were up-modulated after exposure, as was the expression of important membrane proteins such as the scavenger receptors, MHC-II, or the MAC-1 receptor. These results suggest that repeated exposure to low doses of SAS slightly modulates the immune functions of macrophages, which may alter the homeostasis of the immune system.

Evaluation of the immunomodulatory effects of cobalt, copper and magnesium ions in a pro inflammatory environment

Biomaterials and scaffolds for Tissue Engineering are widely used for an effective healing and regeneration. However, the implantation of these scaffolds causes an innate immune response in which the macrophage polarization from M1 (pro-inflammatory) to M2 (anti-inflammatory) phenotype is crucial to avoid chronic inflammation. Recent studies have showed that the use of bioactive ions such as cobalt (Co²⁺), copper (Cu²⁺) and magnesium (Mg²⁺) could improve tissue regeneration, although there is limited evidence on their effect on the macrophage response. Therefore, we investigated the immunomodulatory potential of Co²⁺, Cu²⁺ and Mg²⁺ in macrophage polarization. Our results indicate that Mg²⁺ and concentrations of Cu²⁺ lower than 10 μM promoted the expression of M2 related genes. However, higher concentrations of Cu²⁺ and Co²⁺ (100 μM) stimulated pro-inflammatory marker expression, indicating a concentration dependent effect of these ions. Furthermore, Mg²⁺ were able to decrease M1 marker expression in presence of a mild pro-inflammatory stimulus, showing that Mg²⁺ can be used to modulate the inflammatory response, even though their application can be limited in a strong pro-inflammatory environment.

Time dependent impact of copper oxide nanomaterials on the expression of genes associated with oxidative stress, metal binding, inflammation and mucus secretion in single and co-culture intestinal in vitro models

The potential for ingestion of copper oxide nanomaterials (CuO NMs) is increasing due to their increased exploitation. Investigation of changes in gene expression allows toxicity to be detected at an early stage of NM exposure and can enable investigation of the mechanism of toxicity. Here, undifferentiated Caco-2 cells, differentiated Caco-2 cells, Caco-2/HT29-MTX (mucus secreting) and Caco-2/Raji B (M cell model) co-cultures were exposed to CuO NMs and copper sulphate (CuSO₄) in order to determine their impacts. Cellular responses were measured in terms of production of reactive oxygen species (ROS), the gene expression of an antioxidant (haem oxygenase 1 (HMOX1)), the pro-inflammatory cytokine (interleukin 8 (IL8)), the metal binding (metallothionein 1A and 2A (MT1A and MT2A)) and the mucus secreting (mucin 2 (MUC2)), as well as HMOX-1 protein level. While CuSO₄ induced ROS production in cells, no such effect was observed for CuO NMs. However, these particles did induce an increase in the level of HMOX-1 protein and upregulation of HMOX1, MT2A, IL8 and MUC2 genes in all cell models. In conclusion, the expression of HMOX1, IL8 and MT2A were responsive to CuO NMs at 4 to 12 h post exposure when investigating the toxicity of NMs using intestinal in vitro models. These findings can inform the selection of endpoints, timepoints and models when investigating NM toxicity to the intestine in vitro in the future.

Multiparametric Profiling of Engineered Nanomaterials: Unmasking the Surface Coating Effect

Despite considerable efforts, the properties that drive the cytotoxicity of engineered nanomaterials (ENMs) remain poorly understood. Here, the authors inverstigate a panel of 31 ENMs with different core chemistries and a variety of surface modifications using conventional in vitro assays coupled with omics-based approaches. Cytotoxicity screening and multiplex-based cytokine profiling reveals a good concordance between primary human monocyte-derived macrophages and the human monocyte-like cell line THP-1. Proteomics analysis following a low-dose exposure of cells suggests a nonspecific stress response to ENMs, while microarray-based profiling reveals significant changes in gene expression as a function of both surface modification and core chemistry. Pathway analysis highlights that the ENMs with cationic surfaces that are shown to elicit cytotoxicity downregulated DNA replication and cell cycle responses, while inflammatory responses are upregulated. These findings are validated using cell-based assays. Notably, certain small, PEGylated ENMs are found to be noncytotoxic yet they induce transcriptional responses reminiscent of viruses. In sum, using a multiparametric approach, it is shown that surface chemistry is a key determinant of cellular responses to ENMs. The data also reveal that cytotoxicity, determined by conventional in vitro assays, does not necessarily correlate with transcriptional effects of ENMs.

ZnO and TiO2 nanoparticles alter the ability of Bacillus subtilis to fight against a stress

Due to the physicochemical properties of nanoparticles, the use of nanomaterials increases over time in industrial and medical processes. We herein report the negative impact of nanoparticles, using solid growth conditions mimicking a biofilm, on the ability of Bacillus subtilis to fight against a stress. Bacteria have been exposed to sublethal doses of nanoparticles corresponding to conditions that bacteria may meet in their natural biotopes, the upper layer of soil or the gut microbiome. The analysis of the proteomic data obtained by shotgun mass spectrometry have shown that several metabolic pathways are affected in response to nanoparticles, n-ZnO or n-TiO₂, or zinc salt: the methyglyoxal and thiol metabolisms, the oxidative stress and the stringent responses. Nanoparticles being embedded in the agar medium, these impacts are the consequence of a physiological adaptation rather than a physical cell injury. Overall, these results show that nanoparticles, by altering bacterial physiology and especially the ability to resist to a stress, may have profound influences on a “good bacteria”, Bacillus subtilis, in its natural biotope and moreover, on the global equilibrium of this biotope.

How Reversible Are the Effects of Fumed Silica on Macrophages? A Proteomics-Informed View

Synthetic amorphous silica is one of the most used nanomaterials, and numerous toxicological studies have studied its effects. Most of these studies have used an acute exposure mode to investigate the effects immediately after exposure. However, this exposure modality does not allow the investigation of the persistence of the effects, which is a crucial aspect of silica toxicology, as exemplified by crystalline silica. In this paper, we extended the investigations by studying not only the responses immediately after exposure but also after a 72 h post-exposure recovery phase. We used a pyrolytic silica as the test nanomaterial, as this variant of synthetic amorphous silica has been shown to induce a more persistent inflammation in vivo than precipitated silica. To investigate macrophage responses to pyrolytic silica, we used a combination of proteomics and targeted experiments, which allowed us to show that most of the cellular functions that were altered immediately after exposure to pyrolytic silica at a subtoxic dose, such as energy metabolism and cell morphology, returned to normal at the end of the recovery period. However, some alterations, such as the inflammatory responses and some aldehyde detoxification proteins, were persistent. At the proteomic level, other alterations, such as proteins implicated in the endosomal/lysosomal pathway, were also persistent but resulted in normal function, thus suggesting cellular adaptation.

What Room for Two-Dimensional Gel-Based Proteomics in a Shotgun Proteomics World?

Two-dimensional gel electrophoresis was instrumental in the birth of proteomics in the late 1980s. However, it is now often considered as an outdated technique for proteomics—a thing of the past. Although this opinion may be true for some biological questions, e.g., when analysis depth is of critical importance, for many others, two-dimensional gel electrophoresis-based proteomics still has a lot to offer. This is because of its robustness, its ability to separate proteoforms, and its easy interface with many powerful biochemistry techniques (including western blotting). This paper reviews where and why two-dimensional gel electrophoresis-based proteomics can still be profitably used. It emerges that, rather than being a thing of the past, two-dimensional gel electrophoresis-based proteomics is still highly valuable for many studies. Thus, its use cannot be dismissed on simple fashion arguments and, as usual, in science, the tree is to be judged by the fruit.

Influences of Nanoparticles Characteristics on the Cellular Responses: The Example of Iron Oxide and Macrophages

Iron oxide nanoparticles/microparticles are widely present in a variety of environments, e.g., as a byproduct of steel and iron degradation, as, for example, in railway brakes (e.g., metro station) or in welding fumes. As all particulate material, these metallic nanoparticles are taken up by macrophages, a cell type playing a key role in the innate immune response, including pathogen removal phagocytosis, secretion of free radical species such as nitric oxide or by controlling inflammation via cytokine release. In this paper, we evaluated how macrophages functions were altered by two iron based particles of different size (100 nm and 20 nm). We showed that at high, but subtoxic concentrations (1 mg/mL, large nanoparticles induced stronger perturbations in macrophages functions such as phagocytic capacity (tested with fluorescent latex microspheres) and the ability to respond to bacterial endotoxin lipopolysaccharide stimulus (LPS) in secreting nitric oxide and pro-cytokines (e.g., Interleukin-6 (IL-6) and Tumor Necrosis Factor (TNF)). These stronger effects may correlate with an observed stronger uptake of iron for the larger nanoparticles.

Evaluation of the cytotoxic and cellular proteome impacts of food-grade TiO2 (E171) using simulated gastrointestinal digestions and a tri-culture small intestinal epithelial model

Engineered nanomaterials (ENMs) are widely used in the food industry; however, regulations for ENMs in food are still in the early stages of development due to insufficient health data. This study investigated the cytotoxicity and changes to the proteomic profile in an in vitro small intestinal epithelium model after exposure to digested food models containing the ubiquitous engineered particulate food additive, TiO₂ (E171) with an average size around 110 nm. TiO₂ at 0.75% or 1.5% (w/w) concentrations in either a fasting food model (FFM) or a standardized food model (SFM) based on American diet were digested using an in vitro oral-gastric-small intestinal simulator, and the resulting digestas were applied to a small intestinal epithelium tri-culture cellular model. Effects on cell layer integrity, cytotoxicity, and oxidative stress were assessed. In order to explore the impact on cellular processes beyond basic cytotoxicity, mass spectrometry-based quantitative proteomic analyses of control and exposed tri-culture cells was performed. TiO₂ in FFM, but not in SFM, produced significant, dose-dependent cytotoxicity (24%, p<0.001), and at the higher dose caused significant oxidative stress (1.24-fold, p<0.01), indicative of a food matrix effect. No significant perturbations of the cellular proteome were observed with TiO₂ in either FFM or SFM food models. However, proteins involved in energy metabolism and protein synthesis were up-regulated by digestas from SFM compared to those from FFM, indicative of a food matrix effect on the cellular proteome. Interestingly, the differences in profiles between the two food models was more pronounced in the presence of TiO₂. Together, these results indicate that TiO₂ in a fasting diet may be slightly cytotoxic, and that ingested TiO₂ does not significantly alter the epithelial proteome, whereas the food matrix alone can have a dramatic effect on the proteome.

Effects of Iron Oxide Nanoparticles (γ-Fe2O3) on Liver, Lung and Brain Proteomes following Sub-Acute Intranasal Exposure: A New Toxicological Assessment in Rat Model Using iTRAQ-Based Quantitative Proteomics

Iron Oxide Nanoparticles (IONPs) present unique properties making them one of the most used NPs in the biomedical field. Nevertheless, for many years, growing production and use of IONPs are associated with risks that can affect human and the environment. Thus, it is essential to study the effects of these nanoparticles to better understand their mechanism of action and the molecular perturbations induced in the organism. In the present study, we investigated the toxicological effects of IONPs (γ-Fe2O3) on liver, lung and brain proteomes in Wistar rats. Exposed rats received IONP solution during 7 consecutive days by intranasal instillation at a dose of 10 mg/kg body weight. An iTRAQ-based quantitative proteomics was used to study proteomic variations at the level of the three organs. Using this proteomic approach, we identified 1565; 1135 and 1161 proteins respectively in the brain, liver and lung. Amon them, we quantified 1541; 1125 and 1128 proteins respectively in the brain, liver and lung. Several proteins were dysregulated comparing treated samples to controls, particularly, proteins involved in cytoskeleton remodeling, cellular metabolism, immune system stimulation, inflammation process, response to oxidative stress, angiogenesis, and neurodegenerative diseases.

A Proteomic View of Cellular Responses to Anticancer Quinoline-Copper Complexes

Metal-containing drugs have long been used in anticancer therapies. The mechansims of action of platinum-based drugs are now well-understood, which cannot be said of drugs containing other metals, such as gold or copper. To gain further insights into such mechanisms, we used a classical proteomic approach based on two-dimensional elelctrophoresis to investigate the mechanisms of action of a hydroxyquinoline-copper complex, which shows promising anticancer activities, using the leukemic cell line RAW264.7 as the biological target. Pathway analysis of the modulated proteins highlighted changes in the ubiquitin/proteasome pathway, the mitochondrion, the cell adhesion-cytoskeleton pathway, and carbon metabolism or oxido-reduction. In line with these prteomic-derived hypotheses, targeted validation experiments showed that the hydroxyquinoline-copper complex induces a massive reduction in free glutathione and a strong alteration in the actin cytoskeleton, suggesting a multi-target action of the hydroxyquinoline-copper complex on cancer cells.

Investigating the toxic effects induced by iron oxide nanoparticles on neuroblastoma cell line: an integrative study combining cytotoxic, genotoxic and proteomic tools

Nanomaterials have gained much attention for their use and benefit in several fields. Iron Oxide Nanoparticles (IONPs) have been used in Biomedicine as contrast agents for imaging cancer cells. However, several studies reported the potential toxicity of those nanoparticles in different models, especially in cells. Therefore, in our present study, we investigated the effects of IONPs on the SH-SY5Y neuroblastoma cell line. We carried out cytotoxic and genotoxic studies to evaluate the phenotypic effects, and proteomic investigation to evaluate the molecular effects and the mechanisms by which this kind of NPs could induce toxicity. Our results showed that the use of three different sizes of IONPs (14, 22 and 30 nm) induced cell detachment, cell morphological changes, size, and concentration-dependent IONP internalization and cell mortality. IONPs induced slight genotoxic damage assayed by modified comet assay without affecting cell cycle, mitochondrial function, membrane integrity, intracellular calcium level, and without inducing ROS generation. All the studies were performed to compare also the effects of IONPs to the ferric iron by incubating cells with equivalent concentration of FeCl₃. In all tests, the NPs exhibited more toxicity than the ferric iron. The proteomic analysis followed by gene ontology and pathway analysis evidenced the effects of IONPs on cytoskeleton, cell apoptosis, and cancer development. Our findings provided more information about IONP effects on human cells and especially on cancer cell line.

Comparative contributions of copper nanoparticles and ions to copper bioaccumulation and toxicity in barnacle larvae

Cu nanoparticles (CuNPs) have been widely used in numerous products, and may become a potential threat to marine organisms, but their behavior in the marine environments and potential toxicity to marine organisms remain little known. In the present study, we investigated the behavior of CuNPs in seawater, as well as the toxicity and bioaccumulation of CuNPs and copper sulfate (CuSO₄) in barnacle larvae (Balanus amphitrite), a dominant fouling invertebrate in marine environment. CuNPs tended to aggregate in natural seawater and released Cu ion rapidly into seawater. The aggregation and release were especially higher at a lower concentration of CuNPs, e.g., 94-96% of CuNPs were released as Cu ions at 20 μg/L after 24 h. The larger size of CuNPs (40 nm) tended to display a higher solubility than the 20 nm CuNPs did. Humic acids enhanced the aggregation and inhibited the dissolution of CuNPs, and had a protective effect on the survival of nauplii II at higher Cu concentrations (100-200 μg/L). Comparison of the lethal concentrations showed that CuNPs were generally less toxic to the two stages of barnacle larvae (nauplii II and VI) than the Cu ions. The calculated 48-h LC₅₀ values for nauplii II were 189.5 μg/L, 123.2 μg/L, and 89.8 μg/L for 20 nm CuNPs, 40 nm CuNPs, and CuSO₄, respectively. However, the lethal concentrations of Cu bioaccumulation in the barnacle larvae were comparable between CuNPs and Cu ions when expressed by the actual tissue Cu bioaccumulation. Barnacle larval settlement decreased with an increase of Cu concentrations of both CuNPs and CuSO₄, and was significantly inhibited at 100 μg/L CuSO₄ and 150 μg/L CuNPs. Our results indicated that the toxicity of CuNPs could not be solely explained by the released Cu ions, and both CuNPs and the released Cu ion contributed to their toxicity and bioaccumulation in barnacle larvae.

Utility of macrophages in an antitumor strategy based on the vectorization of iron oxide nanoparticles

Many solid tumors and their metastases are still resistant to current cancer treatments such as chemo- and radiotherapy. The presence of a small population of Cancer Stem Cells in tumors is held responsible for relapses. Moreover, the various physical barriers of the organism (e.g. blood-brain barrier) prevent many drugs from reaching the target cells. In order to alleviate this constraint, we suggest a Trojan horse strategy consisting of intravascular injection of macrophages loaded with therapeutic nanoparticles (an iron nanoparticle-based solution marketed under the name of FERINJECT®) to bring a high quantity of the latter to the tumor. The aim of this article is to assess the response of primary macrophages to FERINJECT® via functional assays in order to ensure that the macrophages loaded with these nanoparticles are still relevant for our strategy. Following this first step, we demonstrate that the loaded macrophages injected into the bloodstream are able to migrate to the tumor site using small-animal imaging. Finally, using synchrotron radiation, we validate an improvement of the radiotherapeutic effect when FERINJECT®-laden macrophages are deposited at the vicinity of cancer cells and irradiated.

Food additives can act as triggering factors in celiac disease: Current knowledge based on a critical review of the literature

Celiac disease (CeD) is an autoimmune disorder, mainly affecting the small intestine, triggered by the ingestion of gluten with the diet in subjects with a specific genetic status. The passage of gluten peptides through the intestinal barrier, the uptake by antigen presenting cells and their presentation to T cells represent essential steps in the pathogenesis of the disease. CeD prevalence varies in different populations, but a tendency to increase has been observed in various studies in recent years. A higher amount of gluten in modern grains could explain this increased frequency, but also food processing could play a role in this phenomenon. In particular, the common use of preservatives such as nanoparticles could intervene in the pathogenesis of CeD, due to their possible effect on the integrity of the intestinal barrier, immune response or microbiota. In fact, these alterations have been reported after exposure to metal nanoparticles, which are commonly used as preservatives or to improve food texture, consistency and color. This review will focus on the interactions between several food additives and the intestine, taking into account data obtained in vitro and in vivo, and analyzing their effect in respect to the development of CeD in genetically predisposed individuals.

Mass spectrometry-based proteomics for system-level characterization of biological responses to engineered nanomaterials

The widespread use of engineered nanomaterials or nanotechnology makes the characterization of biological responses to nanomaterials an important area of research. The application of omics approaches, such as mass spectrometry-based proteomics, has revealed new insights into the cellular responses of exposure to nanomaterials, including how nanomaterials interact and alter cellular pathways. In addition, exposure to engineered nanomaterials often leads to the generation of reactive oxygen species and cellular oxidative stress, which implicates a redox-dependent regulation of cellular responses under such conditions. In this review, we discuss quantitative proteomics-based approaches, with an emphasis on redox proteomics, as a tool for system-level characterization of the biological responses induced by engineered nanomaterials. Graphical abstract ᅟ.

Synthesis methods influence characteristics, behaviour and toxicity of bare CuO NPs compared to bulk CuO and ionic Cu after in vitro exposure of Ruditapes philippinarum hemocytes

Copper oxide (CuO) nanoparticles (NPs) are increasingly investigated, developed and produced for a wide range of industrial and consumer products. Notwithstanding their promising novel applications, concern has been raised that their increased use and disposal could consequently increase their release into marine systems and potentially affect species within. To date the understanding of factors and mechanisms of CuO (nano-) toxicity to marine invertebrates is still limited. Hence, we studied the characteristics and behaviour of two commercially available CuO NPs of similar size, but produced employing distinct synthesis methods, under various environmentally and experimentally relevant conditions. In addition, cell viability and DNA damage, as well as gene expression of detoxification, oxidative stress, inflammatory response, DNA damage repair and cell death mediator markers were studied in primary cultures of hemocytes from the marine clam Ruditapes philippinarum and, where applicable, compared to bulk CuO and ionic Cu (as CuSO₄) behaviour and effects. We found that the synthesis method can influence particle characteristics and behaviour, as well as the toxicity of CuO NPs to Ruditapes philippinarum hemocytes. Our results further indicate that under the tested conditions aggregating behaviour influences the toxicity of CuO NPs by influencing their rate of extra- and intracellular dissolution. In addition, gene expression analysis identified similar transcriptional de-regulation for all tested copper treatments for the here measured suite of genes. Finally, our work highlights various differences in the aggregation and dissolution kinetics of CuO particles under environmental (marine) and cell culture exposure conditions that need consideration when extrapolating in vitro findings.

Toxicity of surface-modified copper oxide nanoparticles in a mouse macrophage cell line: Interplay of particles, surface coating and particle dissolution

The rapid dissolution of copper oxide (CuO) nanoparticles (NPs) with release of ions is thought to be one of the main factors modulating their toxicity. Here we assessed the cytotoxicity of a panel of CuO NPs (12 nm ± 4 nm) with different surface modifications, i.e., anionic sodium citrate (CIT) and sodium ascorbate (ASC), neutral polyvinylpyrrolidone (PVP), and cationic polyethylenimine (PEI), versus the pristine (uncoated) NPs, using a murine macrophage cell line (RAW264.7). Cytotoxicity, reactive oxygen species (ROS) production, and cellular uptake were assessed. The cytotoxicity results were analyzed by the benchmark dose (BMD) method and the NPs were ranked based on BMD₂₀ values. The PEI-coated NPs were found to be the most cytotoxic. Despite the different properties of the coating agents, NP dissolution in cell medium was only marginally affected by surface modification. Furthermore, CuCl₂ (used as an ion control) elicited significantly less cytotoxicity when compared to the CuO NPs. We also observed that the antioxidant, N-acetylcysteine, failed to protect against the cytotoxicity of the uncoated CuO NPs. Indeed, the toxicity of the surface-modified CuO NPs was not directly linked to particle dissolution and subsequent Cu burden in cells, nor to cellular ROS production, although CuO-ASC NPs, which were found to be the least cytotoxic, yielded lower levels of ROS in comparison to pristine NPs. Hierarchical cluster analysis suggested, instead, that the toxicity in the current in vitro model could be explained by synergistic interactions between the NPs, their dissolution, and the toxicity of the coating agents.

Impact of nanoparticles on the Bacillus subtilis (3610) competence

Due to the physicochemical properties of nanoparticles, the use of nanomaterials increases every year in industrial and medical processes. At the same time, the increasing number of bacteria becoming resistant to many antibiotics, mostly by a horizontal gene transfer process, is a major public health concern. We herein report, for the first time, the role of nanoparticles in the physiological induction of horizontal gene transfer in bacteria. Besides the most well-known impacts of nanoparticles on bacteria, i.e. death or oxidative stress, two nanoparticles, n-ZnO and n-TiO₂, significantly and oppositely impact the transformation efficiency of Bacillus subtilis in biofilm growth conditions, by modification of the physiological processes involved in the induction of competence, the first step of transformation. This effect is the consequence of a physiological adaptation rather than a physical cell injury: two oligopeptide ABC transporters, OppABCDF and AppDFABC, are differentially expressed in response to nanoparticles. Interestingly, a third tested nanoparticle, n-Ag, has no significant effect on competence in our experimental conditions. Overall, these results show that nanoparticles, by altering bacterial physiology and especially competence, may have profound influences in unsuspected areas, such as the dissemination of antibiotic resistance in bacteria.

Comparative proteomic analysis of hepatic effects induced by nanosilver, silver ions and nanoparticle coating in rats

The presence of nano-scaled particles in food and food-related products has drawn attention to the oral uptake of nanoparticles and their interactions with biological systems. In the present study, we used a toxicoproteomics approach to allow for the untargeted experimental identification and comparative analysis of cellular responses in rat liver after repeated-dose treatment with silver nanoparticles, ions, and the coating matrix used for particle stabilization. The proteomic analysis revealed treatment-related effects caused by exposure to silver in particulate and ionic form. Both silver species induced similar patterns of signaling and metabolic alterations. Silver-induced cellular alterations comprised, amongst others, proteins involved in metal homeostasis, oxidative stress response, and energy metabolism. However, we discovered that secondary nano-scaled structures were formed from ionic silver. Furthermore, also the coating matrix alone gave rise to the formation of nano-scaled particles. The present data confirm, complement, and extend previous knowledge on silver toxicity in rodent liver by providing a comprehensive proteomic data set. The observation of secondary particle formation from non-particle controls underlines the difficulties in separating particle-, ion-, and matrix coating-related effects in biological systems. Awareness of this issue will support proper evaluation of nanotoxicology-related data in the future.

Role of omics techniques in the toxicity testing of nanoparticles

Nanotechnology is regarded as a key technology of the twenty-first century. Despite the many advantages of nanotechnology it is also known that engineered nanoparticles (NPs) may cause adverse health effects in humans. Reports on toxic effects of NPs relay mainly on conventional (phenotypic) testing but studies of changes in epigenome, transcriptome, proteome, and metabolome induced by NPs have also been performed. NPs most relevant for human exposure in consumer, health and food products are metal, metal oxide and carbon-based NPs. They were also studied quite frequently with omics technologies and an overview of the study results can serve to answer the question if screening for established targets of nanotoxicity (e.g. cell death, proliferation, oxidative stress, and inflammation) is sufficient or if omics techniques are needed to reveal new targets. Regulated pathways identified by omics techniques were confirmed by phenotypic assays performed in the same study and comparison of particle types and cells by the same group indicated a more cell/organ-specific than particle specific regulation pattern. Between different studies moderate overlap of the regulated pathways was observed and cell-specific regulation is less obvious. The lack of standardization in particle exposure, in omics technologies, difficulties to translate mechanistic data to phenotypes and comparison with human in vivo data currently limit the use of these technologies in the prediction of toxic effects by NPs.

Omics Approaches for Identifying Physiological Adaptations to Genome Instability in Aging

DNA damage causally contributes to aging and age-related diseases. The declining functioning of tissues and organs during aging can lead to the increased risk of succumbing to aging-associated diseases. Congenital syndromes that are caused by heritable mutations in DNA repair pathways lead to cancer susceptibility and accelerated aging, thus underlining the importance of genome maintenance for withstanding aging. High-throughput mass-spectrometry-based approaches have recently contributed to identifying signalling response networks and gaining a more comprehensive understanding of the physiological adaptations occurring upon unrepaired DNA damage. The insulin-like signalling pathway has been implicated in a DNA damage response (DDR) network that includes epidermal growth factor (EGF)-, AMP-activated protein kinases (AMPK)- and the target of rapamycin (TOR)-like signalling pathways, which are known regulators of growth, metabolism, and stress responses. The same pathways, together with the autophagy-mediated proteostatic response and the decline in energy metabolism have also been found to be similarly regulated during natural aging, suggesting striking parallels in the physiological adaptation upon persistent DNA damage due to DNA repair defects and long-term low-level DNA damage accumulation occurring during natural aging. These insights will be an important starting point to study the interplay between signalling networks involved in progeroid syndromes that are caused by DNA repair deficiencies and to gain new understanding of the consequences of DNA damage in the aging process.

Protein Corona Analysis of Silver Nanoparticles Links to Their Cellular Effects

The breadth of applications of nanoparticles and the access to food-associated consumer products containing nanosized materials lead to oral human exposure to such particles. In biological fluids nanoparticles dynamically interact with biomolecules and form a protein corona. Knowledge about the protein corona is of great interest for understanding the molecular effects of particles as well as their fate inside the human body. We used a mass spectrometry-based toxicoproteomics approach to elucidate mechanisms of toxicity of silver nanoparticles and to comprehensively characterize the protein corona formed around silver nanoparticles in Caco-2 human intestinal epithelial cells. Results were compared with respect to the cellular function of proteins either affected by exposure to nanoparticles or present in the protein corona. A transcriptomic data set was included in the analyses in order to obtain a combined multiomics view of nanoparticle-affected cellular processes. A relationship between corona proteins and the proteomic or transcriptomic responses was revealed, showing that differentially regulated proteins or transcripts were engaged in the same cellular signaling pathways. Protein corona analyses of nanoparticles in cells might therefore help in obtaining information about the molecular consequences of nanoparticle treatment.

Differential proteomics highlights macrophage-specific responses to amorphous silica nanoparticles

The technological and economic benefits of engineered nanomaterials may be offset by their adverse effects on living organisms. One of the highly produced nanomaterials under such scrutiny is amorphous silica nanoparticles, which are known to have an appreciable, although reversible, inflammatory potential. This is due to their selective toxicity toward macrophages, and it is thus important to study the cellular responses of this cell type to silica nanoparticles to better understand the direct or indirect adverse effects of nanosilica. We have here studied the responses of the RAW264.7 murine macrophage cells and of the control MPC11 plasma cells to subtoxic concentrations of nanosilica, using a combination of proteomic and targeted approaches. This allowed us to document alterations in the cellular cytoskeleton, in the phagocytic capacity of the cells as well as their ability to respond to bacterial stimuli. More surprisingly, silica nanoparticles also induce a greater sensitivity of macrophages to DNA alkylating agents, such as styrene oxide, even at doses which do not induce any appreciable cell death.

Antibacterial and Biocompatible Titanium-Copper Oxide Coating May Be a Potential Strategy to Reduce Periprosthetic Infection: An In Vitro Study

BACKGROUND

Periprosthetic infections are devastating for patients and more efficacious preventive strategies are needed. Surface-modified implants using antibacterial coatings represent an option to cope with this problem; however, manufacturing limitations and cytotoxicity have curbed clinical translation. Among metals with antibacterial properties, copper has shown superior in vitro antibacterial performance while maintaining an acceptable cytotoxicity profile. A thin film containing copper could prevent early biofilm formation to limit periprosthetic infections. This pilot study presents the in vitro antibacterial effect, cytotoxicity, and copper ion elution pattern of a thin film of titanium-copper oxide (TiCuO).

QUESTIONS/PURPOSES

(1) Do titanium alloy (Ti6Al4V) discs coated with a thin film of TiCuO reduce Staphylococcus epidermidis biofilm and planktonic cell density compared with uncoated discs? (2) Do Ti6Al4V discs coated with a thin film of TiCuO affect normal human osteoblast viability compared with untreated cells? (3) Is copper ion concentration generated by coated discs lower than previously published copper ion concentrations that cause 50% toxicity in similar human cell lines in vitro (TC50)?

METHODS

Ninety Ti6Al4V discs (12.5 mm diameter; 1.25 mm thick) were used in this study. Seventy-two Ti6Al4V discs were coated with a thin film of either titanium oxide (TiO) or TiCuO containing 20%, 40%, or 80% copper using high-power impulse magnetron sputtering (HiPIMS). Eighteen Ti6Al4V discs remained uncoated for control purposes. We tested antibacterial properties of S epidermidis grown on discs in wells containing growth medium. After 24 hours, planktonic bacteria as well as biofilms removed by sonication were quantitatively cultured. Annexin/Pi staining was used to quantify in vitro normal human osteoblast cell viability at 24 hours and Day 7, respectively. Copper elution was measured at Days 1, 2, 3, 7, 14, and 28 using an inductively coupled plasma mass spectrometer to analyze aliquots of culture medium. Copper ion concentration achieved at 24 hours was compared with previously published TC50 for gingival fibroblast, a phenotypically similar cell line with available data regarding copper ion exposure.

RESULTS

Discs coated with TiCuO 80% copper showed greater biofilm and planktonic cell density reduction when compared with other tested compositions (analysis of variance [ANOVA]; p < 0.001). Discs coated with TiCuO 80% copper showed mean biofilm and planktonic cell density of 4.0 log₁₀ (SD = 0.4) and 5.7 log₁₀ (SD = 0.2). Discs coated with TiCuO 80% showed a mean difference in biofilm and planktonic cell density of 2.5 log₁₀ (95% confidence interval [CI], 1.9-3.1 log_10; p < 0.001) and 1.2 (95% CI, 0.6-1.8; p < 0.001), respectively, when compared with uncoated discs. Normal human osteoblast viability did not differ among all groups at 24 hours (ANOVA; p = 0.2) and Day 7 (ANOVA; p = 0.7). Discs coated with TiCuO 80% copper showed a mean difference (95% CI) in relative cell viability (%) at 24 hours and Day 7 of 31.1 (95% CI, -19.4 to 81.7; p = 0.4) and -5.0 (95% CI, -7.8 to 17.9; p = 0.9), respectively, when compared with untreated cells. For all TiCuO-coated discs, copper ion elution peaked at 24 hours and slowly decreased in a curvilinear fashion to nearly undetectable levels by Day 28. Discs coated with TiCuO 80% copper showed mean copper ion concentration at 24 hours of 269.4 µmol/L (SD = 25.2 µmol/L) and this concentration was lower than previously published TC50 for similar human cell lines at 24 hours (344 µmol/L, SEM = 44 µmol/L).

CONCLUSIONS

This pilot study demonstrates a proof of concept that a thin-film implant coating with TiCuO can provide a potent local antibacterial environment while remaining relatively nontoxic to a human osteoblast cell line. Further research in an animal model will be necessary to establish efficacy and safety of this technique and whether it might be useful in the design of implants.

CLINICAL RELEVANCE

A thin film coating with TiCuO demonstrates high antibacterial activity and low cellular cytotoxicity to human osteoblasts in vitro. Taken together, these properties represent a potential strategy for preventing periprosthetic infection if further work in animal models can confirm these results in vivo.

Green synthesis of silver nanoparticles via plant extracts: beginning a new era in cancer theranostics

With the development of the latest technologies, scientists are looking to design novel strategies for the treatment and diagnosis of cancer. Advances in medicinal plant research and nanotechnology have attracted many researchers to the green synthesis of metallic nanoparticles due to its several advantages over conventional synthesis (simple, fast, energy efficient, one pot processes, safer, economical and biocompatibility). Medicinally active plants have proven to be the best reservoirs of diverse phytochemicals for the synthesis of biogenic silver nanoparticles (AgNPs). In this review, we discuss mechanistic advances in the synthesis and optimization of AgNPs from plant extracts. Moreover, we have thoroughly discussed the recent developments and milestones achieved in the use of biogenic AgNPs as cancer theranostic agents and their proposed mechanism of action. Anticipating all of the challenges, we hope that biogenic AgNPs may become a potential cancer theranostic agent in the near future.

Copper oxide nanoparticle toxicity profiling using untargeted metabolomics

BACKGROUND

The rapidly increasing number of engineered nanoparticles (NPs), and products containing NPs, raises concerns for human exposure and safety. With this increasing, and ever changing, catalogue of NPs it is becoming more difficult to adequately assess the toxic potential of new materials in a timely fashion. It is therefore important to develop methods which can provide high-throughput screening of biological responses. The use of omics technologies, including metabolomics, can play a vital role in this process by providing relatively fast, comprehensive, and cost-effective assessment of cellular responses. These techniques thus provide the opportunity to identify specific toxicity pathways and to generate hypotheses on how to reduce or abolish toxicity.

RESULTS

We have used untargeted metabolome analysis to determine differentially expressed metabolites in human lung epithelial cells (A549) exposed to copper oxide nanoparticles (CuO NPs). Toxicity hypotheses were then generated based on the affected pathways, and critically tested using more conventional biochemical and cellular assays. CuO NPs induced regulation of metabolites involved in oxidative stress, hypertonic stress, and apoptosis. The involvement of oxidative stress was clarified more easily than apoptosis, which involved control experiments to confirm specific metabolites that could be used as standard markers for apoptosis; based on this we tentatively propose methylnicotinamide as a generic metabolic marker for apoptosis.

CONCLUSIONS

Our findings are well aligned with the current literature on CuO NP toxicity. We thus believe that untargeted metabolomics profiling is a suitable tool for NP toxicity screening and hypothesis generation.

Nanomaterial and toxicity: what can proteomics tell us about the nanotoxicology?

1. In the last few years, a substantial scientific work is focused to identify the potential toxicity of nanomaterials by studying the cellular pathways under in vitro and in vivo conditions. Owing to high surface area to volume ratio nanoparticles (NPs) can pass through cell membranes which might be responsible for creating adverse interactions in biological systems. Simultaneously, researchers are also interested to assess the fate of NP inside the living system, which may lead to altered protein expression as well as protein corona formation. 2. According to published reports, NP-mediated toxicity involves altered cellular system including cell morphology, cell differentiation, cell metabolism, cell mobility, cellular immunity, which is derived from the side effects of nanoformulation and leading to apoptosis and necrosis. These results indicate the existence of potential toxic effect of these particles to human health. 3. The advent of proteomics with sophisticated technical improvement coupled with advanced bioinformatics has led to identify altered proteins due to nanomaterial exposure that could provide a new avenue to biomarker discovery. 4. This review aims to provide the current status of safe production and use of nanomaterials.

Therapeutic application of anti-angiogenic nanomaterials in cancers

Angiogenesis, the formation of new blood vessels from pre-existing vasculature, plays a vital role in physiological and pathological processes (embryonic development, wound healing, tumor growth and metastasis). The overall balance of angiogenesis inside the human body is maintained by pro- and anti-angiogenic signals. The processes by which drugs inhibit angiogenesis as well as tumor growth are called the anti-angiogenesis technique, a most promising cancer treatment strategy. Over the last couple of decades, scientists have been developing angiogenesis inhibitors for the treatment of cancers. However, conventional anti-angiogenic therapy has several limitations including drug resistance that can create problems for a successful therapeutic strategy. Therefore, a new comprehensive treatment strategy using antiangiogenic agents for the treatment of cancer is urgently needed. Recently researchers have been developing and designing several nanoparticles that show anti-angiogenic properties. These nanomedicines could be useful as an alternative strategy for the treatment of various cancers using anti-angiogenic therapy. In this review article, we critically focus on the potential application of anti-angiogenic nanomaterial and nanoparticle based drug/siRNA/peptide delivery systems in cancer therapeutics. We also discuss the basic and clinical perspectives of anti-angiogenesis therapy, highlighting its importance in tumor angiogenesis, current status and future prospects and challenges.

Copper oxide nanoparticles recruit macrophages and modulate nitric oxide, proinflammatory cytokines and PGE2 production through arginase activation

AIM

In the present study, we examine the effects of copper oxide nanoparticles (CuNP) on macrophage immune response and the signaling pathways involved.

MATERIALS & METHODS

A peritonitis model was used to determine in vivo immune cells recruitment, while primary macrophages were used as an in vitro model for the cellular and molecular analysis.

RESULTS

In vivo, CuNP induce significant macrophages recruitment to the site of injection. In vitro, in LPS-stimulated primary macrophages, the co-treatment with CuNP inhibited the production of NO in a dose-dependent manner. The mechanism underlying NO and proinflammatory cytokines inhibition was associated with an increased arginase activity. Macrophage stimulation with CuNP did not provoke any cytokine secretion; however, arginase inhibition promoted TNFα and MIP-1β production. In addition, CuNP induced the expression of COX-2 and the production of PGE2 through arginase activation.

CONCLUSION

Our results demonstrate that CuNP activate arginase and suppress macrophage innate immune response.

In vitro toxicity, apoptosis and antimicrobial effects of phyto-mediated copper oxide nanoparticles

Herein, copper oxide nanoparticles (CuONPs) are proposed for widespread use in emerging biomedical applications.

Molecular responses of alveolar epithelial A549 cells to chronic exposure to titanium dioxide nanoparticles: A proteomic view

Although the biological effects of titanium dioxide nanoparticles (TiO2-NPs) have been studied for more than two decades, the mechanisms governing their toxicity are still unclear. We applied 2D-gel proteomics analysis on A549 epithelial alveolar cells chronically exposed for 2months to 2.5 or 50μg/mL of deeply characterized TiO2-NPs, in order to obtain comprehensive molecular responses that may reflect functional outcomes. We show that exposure to TiO2-NPs impacts the abundance of 30 protein species, corresponding to 22 gene products. These proteins are involved in glucose metabolism, trafficking, gene expression, mitochondrial function, proteasome activity and DNA damage response. Besides, our results suggest that p53 pathway is activated, slowing down cell cycle progression and reducing cell proliferation rate. Moreover, we report increased content of chaperones-related proteins, which suggests homeostasis re-establishment. Finally, our results highlight that chronic exposure to TiO2-NPs affects the same cellular functions as acute exposure to TiO2-NPs, although lower exposure concentrations and longer exposure times induce more intense cellular response.

BIOLOGICAL SIGNIFICANCE

Our results make possible the identification of new mechanisms that explain TiO2-NP toxicity upon long-term, in vitro exposure of A549 cells. It is the first article describing -omics results obtained with this experimental strategy. We show that this long-term exposure modifies the cellular content of proteins involved in functions including mitochondrial activity, intra- and extracellular trafficking, proteasome activity, glucose metabolism, and gene expression. Moreover we observe modification of content of proteins that activate the p53 pathway, which suggest the induction of a DNA damage response. Technically, our results show that exposure of A549 cells to a high concentration of TiO2-NPs leads to the identification of modulations of the same functional categories than exposure to low, more realistic concentrations. Still the intensity differs between these two exposure scenarios. We also show that chronic exposure to TiO2-NPs induces the modulation of cellular functions that have already been reported in the literature as being impacted in acute exposure scenarios. This proves that the exposure protocol in in vitro experiments related to nanoparticle toxicology might be cautiously chosen since inappropriate scenario may lead to inappropriate and/or incomplete conclusions.

Zinc oxide induces the stringent response and major reorientations in the central metabolism of Bacillus subtilis

Microorganisms, such as bacteria, are one of the first targets of nanoparticles in the environment. In this study, we tested the effect of two nanoparticles, ZnO and TiO2, with the salt ZnSO4 as the control, on the Gram-positive bacterium Bacillus subtilis by 2D gel electrophoresis-based proteomics. Despite a significant effect on viability (LD50), TiO2 NPs had no detectable effect on the proteomic pattern, while ZnO NPs and ZnSO4 significantly modified B. subtilis metabolism. These results allowed us to conclude that the effects of ZnO observed in this work were mainly attributable to Zn dissolution in the culture media. Proteomic analysis highlighted twelve modulated proteins related to central metabolism: MetE and MccB (cysteine metabolism), OdhA, AspB, IolD, AnsB, PdhB and YtsJ (Krebs cycle) and XylA, YqjI, Drm and Tal (pentose phosphate pathway). Biochemical assays, such as free sulfhydryl, CoA-SH and malate dehydrogenase assays corroborated the observed central metabolism reorientation and showed that Zn stress induced oxidative stress, probably as a consequence of thiol chelation stress by Zn ions. The other patterns affected by ZnO and ZnSO4 were the stringent response and the general stress response. Nine proteins involved in or controlled by the stringent response showed a modified expression profile in the presence of ZnO NPs or ZnSO4: YwaC, SigH, YtxH, YtzB, TufA, RplJ, RpsB, PdhB and Mbl. An increase in the ppGpp concentration confirmed the involvement of the stringent response during a Zn stress. All these metabolic reorientations in response to Zn stress were probably the result of complex regulatory mechanisms including at least the stringent response via YwaC.