Perinatal foodborne titanium dioxide exposure-mediated dysbiosis predisposes mice to develop colitis through life

BACKGROUND

Perinatal exposure to titanium dioxide (TiO2), as a foodborne particle, may influence the intestinal barrier function and the susceptibility to develop inflammatory bowel disease (IBD) later in life. Here, we investigate the impact of perinatal foodborne TiO2 exposure on the intestinal mucosal function and the susceptibility to develop IBD-associated colitis. Pregnant and lactating mother mice were exposed to TiO2 until pups weaning and the gut microbiota and intestinal barrier function of their offspring was assessed at day 30 post-birth (weaning) and at adult age (50 days). Epigenetic marks was studied by DNA methylation profile measuring the level of 5-methyl-2'-deoxycytosine (5-Me-dC) in DNA from colic epithelial cells. The susceptibility to develop IBD has been monitored using dextran-sulfate sodium (DSS)-induced colitis model. Germ-free mice were used to define whether microbial transfer influence the mucosal homeostasis and subsequent exacerbation of DSS-induced colitis.

RESULTS

In pregnant and lactating mice, foodborne TiO2 was able to translocate across the host barriers including gut, placenta and mammary gland to reach embryos and pups, respectively. This passage modified the chemical element composition of foetus, and spleen and liver of mothers and their offspring. We showed that perinatal exposure to TiO2 early in life alters the gut microbiota composition, increases the intestinal epithelial permeability and enhances the colonic cytokines and myosin light chain kinase expression. Moreover, perinatal exposure to TiO2 also modifies the abilities of intestinal stem cells to survive, grow and generate a functional epithelium. Maternal TiO2 exposure increases the susceptibility of offspring mice to develop severe DSS-induced colitis later in life. Finally, transfer of TiO2-induced microbiota dysbiosis to pregnant germ-free mice affects the homeostasis of the intestinal mucosal barrier early in life and confers an increased susceptibility to develop colitis in adult offspring.

CONCLUSIONS

Our findings indicate that foodborne TiO2 consumption during the perinatal period has negative long-lasting consequences on the development of the intestinal mucosal barrier toward higher colitis susceptibility. This demonstrates to which extent environmental factors influence the microbial-host interplay and impact the long-term mucosal homeostasis.

Nanomaterial genotoxicity evaluation using the high-throughput p53-binding protein 1 (53BP1) assay

Toxicity evaluation of engineered nanomaterials is challenging due to the ever increasing number of materials and because nanomaterials (NMs) frequently interfere with commonly used assays. Hence, there is a need for robust, high-throughput assays with which to assess their hazard potential. The present study aimed at evaluating the applicability of a genotoxicity assay based on the immunostaining and foci counting of the DNA repair protein 53BP1 (p53-binding protein 1), in a high-throughput format, for NM genotoxicity assessment. For benchmarking purposes, we first applied the assay to a set of eight known genotoxic agents, as well as X-ray irradiation (1 Gy). Then, a panel of NMs and nanobiomaterials (NBMs) was evaluated with respect to their impact on cell viability and genotoxicity, and to their potential to induce reactive oxygen species (ROS) production. The genotoxicity recorded using the 53BP1 assay was confirmed using the micronucleus assay, also scored via automated (high-throughput) microscopy. The 53BP1 assay successfully identified genotoxic compounds on the HCT116 human intestinal cell line. None of the tested NMs showed any genotoxicity using the 53BP1 assay, except the positive control consisting in (CoO)(NiO) NMs, while only TiO2 NMs showed positive outcome in the micronucleus assay. Only Fe3O4 NMs caused significant elevation of ROS, not correlated to DNA damage. Therefore, owing to its adequate predictivity of the genotoxicity of most of the tested benchmark substance and its ease of implementation in a high throughput format, the 53BP1 assay could be proposed as a complementary high-throughput screening genotoxicity assay, in the context of the development of New Approach Methodologies.

Hazard, Distribution and Exposure of Particulate Pollution from Indoor and Outdoor Environments

Air is an essential natural resource for life [...].

Data-Driven Quantitative Intrinsic Hazard Criteria for Nanoproduct Development in a Safe-by-Design Paradigm: A Case Study of Silver Nanoforms

The current European (EU) policies, that is, the Green Deal, envisage safe and sustainable practices for chemicals, which include nanoforms (NFs), at the earliest stages of innovation. A theoretically safe and sustainable by design (SSbD) framework has been established from EU collaborative efforts toward the definition of quantitative criteria in each SSbD dimension, namely, the human and environmental safety dimension and the environmental, social, and economic sustainability dimensions. In this study, we target the safety dimension, and we demonstrate the journey toward quantitative intrinsic hazard criteria derived from findable, accessible, interoperable, and reusable data. Data were curated and merged for the development of new approach methodologies, that is, quantitative structure-activity relationship models based on regression and classification machine learning algorithms, with the intent to predict a hazard class. The models utilize system (i.e., hydrodynamic size and polydispersity index) and non-system (i.e., elemental composition and core size)-dependent nanoscale features in combination with biological in vitro attributes and experimental conditions for various silver NFs, functional antimicrobial textiles, and cosmetics applications. In a second step, interpretable rules (criteria) followed by a certainty factor were obtained by exploiting a Bayesian network structure crafted by expert reasoning. The probabilistic model shows a predictive capability of ≈78% (average accuracy across all hazard classes). In this work, we show how we shifted from the conceptualization of the SSbD framework toward the realistic implementation with pragmatic instances. This study reveals (i) quantitative intrinsic hazard criteria to be considered in the safety aspects during synthesis stage, (ii) the challenges within, and (iii) the future directions for the generation and distillation of such criteria that can feed SSbD paradigms. Specifically, the criteria can guide material engineers to synthesize NFs that are inherently safer from alternative nanoformulations, at the earliest stages of innovation, while the models enable a fast and cost-efficient in silico toxicological screening of previously synthesized and hypothetical scenarios of yet-to-be synthesized NFs.

Physicochemical Transformations of Silver Nanoparticles in the Oro-Gastrointestinal Tract Mildly Affect Their Toxicity to Intestinal Cells In Vitro: An AOP-Oriented Testing Approach

The widespread use of silver nanoparticles (Ag NPs) in food and consumer products suggests the relevance of human oral exposure to these nanomaterials (NMs) and raises the possibility of adverse effects in the gastrointestinal tract. The aim of this study was to investigate the toxicity of Ag NPs in a human intestinal cell line, either uncoated or coated with polyvinylpyrrolidone (Ag PVP) or hydroxyethylcellulose (Ag HEC) and digested in simulated gastrointestinal fluids. Physicochemical transformations of Ag NPs during the different stages of in vitro digestion were identified prior to toxicity assessment. The strategy for evaluating toxicity was constructed on the basis of adverse outcome pathways (AOPs) showing Ag NPs as stressors. It consisted of assessing Ag NP cytotoxicity, oxidative stress, genotoxicity, perturbation of the cell cycle and apoptosis. Ag NPs caused a concentration-dependent loss of cell viability and increased the intracellular level of reactive oxygen species as well as DNA damage and perturbation of the cell cycle. In vitro digestion of Ag NPs did not significantly modulate their toxicological impact, except for their genotoxicity. Taken together, these results indicate the potential toxicity of ingested Ag NPs, which varied depending on their coating but did not differ from that of non-digested NPs.

Selective plane illumination microscope dedicated to volumetric imaging in microfluidic chambers

In this article, we are presenting an original selective plane illumination fluorescence microscope dedicated to image "Organ-on-chip"-like biostructures in microfluidic chips. In order to be able to morphologically analyze volumetric samples in development at the cellular scale inside microfluidic chambers, the setup presents a compromise between relatively large field of view (∼ 200 µm) and moderate resolution (∼ 5 µm). The microscope is based on a simple design, built around the chip and its microfluidic environment to allow 3D imaging inside the chip. In particular, the sample remains horizontally avoiding to disturb the fluidics phenomena. The experimental setup, its optical characterization and the first volumetric images are reported.

Magnetic particles for triggering insulin release in INS-1E cells subjected to a rotating magnetic field

Diabetes is a major global health threat. Both academics and industry are striving to develop effective treatments for this disease. In this work, we present a new approach to induce insulin release from β-islet pancreatic cells (INS-1E) by mechanical stimulation. Two types of experiments were carried out. First, a local stimulation was performed by dispersing anisotropic magnetic particles within the cell medium, which settled down almost immediately on cell plasma membranes. Application of a low frequency magnetic field (up to 40 Hz) generated by a custom-made magnetic device resulted in oscillations of these particles, which then exerted a mechanical constraint on the cell plasma membranes. The second type of experiment consisted of a global stimulation, where cells were grown on magneto-elastic membranes composed of a biocompatible polymer with embedded magnetic particles. Upon application of a rotating magnetic field, magnetic particles within the membrane were attracted towards the field source, resulting in the membrane's vibrations being transmitted to the cells grown on it. In both experiments, the cell response to these mechanical stimulations caused by application of the variable magnetic field was quantified via the measurement of insulin release in the growth medium. We demonstrated that the mechanical action induced by the motion of magnetic particles or by membrane vibrations was an efficient stimulus for insulin granule secretion from β-cells. This opens a wide range of possible applications including the design of a system which triggers insulin secretion by β-islet pancreatic cells on demand.

P01.15.A Longitudinal assessment of neurocognition and quality of life in low-grade glioma patients receiving first-line Temozolomide

Background

While maximal safe resection is the first therapeutic option in patients with newly-diagnosed diffuse low-grade glioma (DLGG), the timing and choice of further treatments (chemotherapy, radiation therapy or combinations of both) remain controversial. Because the expected survival is long in these young patients, the oncological impact of treatments must be balanced with the possible side effects, in particular regarding neurocognitive functioning and quality of life (QoL). Temozolomide (TMZ), an alkylating agent, is widely used in this setting. Here we aimed at evaluating the feasibility of a longitudinal neurocognitive and QoL assessment in DLGG patients receiving TMZ.

Material and Methods

We conducted a prospective study including adult DLGG patients receiving TMZ as first-line treatment after surgical resection(s) or biopsy. Neurocognition and QoL were evaluated longitudinally until progression. The feasibility was evaluated in terms of participation and compliance of a complete neurocognitive and QoL assessment (defined as the completion of these assessments at baseline, 6 months and 12 months). Secondary objectives were the description of the proportion of patients with changes in neurocognitive or QoL scores on TMZ.

Results

Of 29 eligible patients, 26 accepted to enter the study (participation rate 86.7%): 57.7% men, median age 45y. Tumor type was distributed as follows: astrocytoma, IDH-mutant 13/26, astrocytoma, IDH wild-type 1/26 and oligodendroglioma, IDH mutant and 1p19q codeleted 12/26. The compliance rate was 95.6% (evaluable in 23 patients as 3 patients had tumor progression within the first 12 months of TMZ). After TMZ, 13.6% of patients experienced a decline of the MoCA score as compared to baseline (from normal to abnormal). Cognitive complaints according to the FACT-COG assessment were stable for 90.9%. The complete cognitive and QoL evaluations (baseline and after 12 months of TMZ) will be presented.

Conclusion

Our data shows that a longitudinal evaluation of cognition and QoL is feasible in low-grade glioma patients. It suggests that first-line TMZ does not negatively affect neurocognition and QoL. These results must be evaluated in the long-term setting (evaluations ongoing) and confirmed in a larger, multicenter cohort.

Changes of physico-chemical properties of nano-biomaterials by digestion fluids affect the physiological properties of epithelial intestinal cells and barrier models

Background

The widespread use of nano-biomaterials (NBMs) has increased the chance of human exposure. Although ingestion is one of the major routes of exposure to NBMs, it is not thoroughly studied to date. NBMs are expected to be dramatically modified following the transit into the oral-gastric-intestinal (OGI) tract. How these transformations affect their interaction with intestinal cells is still poorly understood. NBMs of different chemical nature—lipid-surfactant nanoparticles (LSNPs), carbon nanoparticles (CNPs), surface modified Fe₃O₄ nanoparticles (FNPs) and hydroxyapatite nanoparticles (HNPs)—were treated in a simulated human digestive system (SHDS) and then characterised. The biological effects of SHDS-treated and untreated NBMs were evaluated on primary (HCoEpiC) and immortalised (Caco-2, HCT116) epithelial intestinal cells and on an intestinal barrier model.

Results

The application of the in vitro SDHS modified the biocompatibility of NBMs on gastrointestinal cells. The differences between SHDS-treated and untreated NBMs could be attributed to the irreversible modification of the NBMs in the SHDS. Aggregation was detected for all NBMs regardless of their chemical nature, while pH- or enzyme-mediated partial degradation was detected for hydroxyapatite or polymer-coated iron oxide nanoparticles and lipid nanoparticles, respectively. The formation of a bio-corona, which contains proteases, was also demonstrated on all the analysed NBMs. In viability assays, undifferentiated primary cells were more sensitive than immortalised cells to digested NBMs, but neither pristine nor treated NBMs affected the intestinal barrier viability and permeability. SHDS-treated NBMs up-regulated the tight junction genes (claudin 3 and 5, occludin, zonula occludens 1) in intestinal barrier, with different patterns between each NBM, and increase the expression of both pro- and anti-inflammatory cytokines (IL-1β, TNF-α, IL-22, IL-10). Notably, none of these NBMs showed any significant genotoxic effect.

Conclusions

Overall, the results add a piece of evidence on the importance of applying validated in vitro SHDS models for the assessment of NBM intestinal toxicity/biocompatibility. We propose the association of chemical and microscopic characterization, SHDS and in vitro tests on both immortalised and primary cells as a robust screening pipeline useful to monitor the changes in the physico-chemical properties of ingested NBMs and their effects on intestinal cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00491-w.

Safe-by-design strategies for lowering the genotoxicity and pulmonary inflammation of multiwalled carbon nanotubes: Reduction of length and the introduction of COOH groups

Potentially, the toxicity of multiwalled carbon nanotubes (MWCNTs) can be reduced in a safe-by-design strategy. We investigated if genotoxicity and pulmonary inflammation of MWCNTs from the same batch were lowered by a) reducing length and b) introducing COOH-groups into the structure. Mice were administered: 1) long and pristine MWCNT (CNT-long) (3.9 μm); 2) short and pristine CNT (CNT-short) (1 μm); 3) CNT modified with high ratio COOH-groups (CNT-COOH-high); 4) CNT modified with low ratio COOH-groups (CNT-COOH-low). MWCNTs were dosed by intratracheal instillation at 18 or 54 μg/mouse (∼0.9 and 2.7 mg/kg bw). Neutrophils numbers were highest after CNT-long exposure, and both shortening the MWCNT and addition of COOH-groups lowered pulmonary inflammation (day 1 and 28). Likewise, CNT-long induced genotoxicity, which was absent with CNT-short and after introduction of COOH groups. In conclusion, genotoxicity and pulmonary inflammation of MWCNTs were lowered, but not eliminated, by shortening the fibres or introducing COOH-groups.

Titanium dioxide particles from the diet: involvement in the genesis of inflammatory bowel diseases and colorectal cancer

The gastrointestinal tract is a complex interface between the external environment and the immune system. Its ability to control uptake across the mucosa and to protect the body from damage of harmful substances from the lumen is defined as the intestinal barrier function (IBF). The IBF involves four elements: the intestinal microbiota, the mucus layer, the epithelium and the immune system. Its dysfunction is linked with human diseases including inflammatory, metabolic, infectious, autoimmune and neurologic disorders. Most of these diseases are complex and involve genetic, psychological and environmental factors. Over the past 10 years, many genetic polymorphisms predisposing to inflammatory bowel disease (IBD) have been identified. Yet, it is now clear that they are insufficient to explain the onset of these chronic diseases. Although it has been evidenced that some environmental factors such as cigarette smoking or carbohydrate intake are associated with IBD, other environmental factors also present potential health risks such as ingestion of food additives introduced in the human diet, including those composed of mineral particles, by altering the four elements of the intestinal barrier function. The aim of this review is to provide a critical opinion on the potential of TiO₂ particles, especially when used as a food additive, to alter the four elements of the intestinal barrier function, and consequently to evaluate if this additive would likely play a role in the development and/or exacerbation of IBD.

Evaluation of the Dermal Toxicity of InZnP Quantum Dots Before and After Accelerated Weathering: Toward a Safer-By-Design Strategy

Quantum dots (QDs) are colloidal fluorescent semiconductor nanocrystals with exceptional optical properties. Their widespread use, particularly in light-emitting diodes (LEDs), displays, and photovoltaics, is questioning their potential toxicity. The most widely used QDs are CdSe and CdTe QDs, but due to the toxicity of cadmium (Cd), their use in electrical and electronic equipment is now restricted in the European Union through the Restriction of hazardous substances in electrical and electronic equipment (RoHS) directive. This has prompted the development of safer alternatives to Cd-based QDs; among them, InP QDs are the most promising ones. We recently developed RoHS-compliant QDs with an alloyed core composed of InZnP coated with a Zn(Se,S) gradient shell, which was further coated with an additional ZnS shell to protect the QDs from oxidative surface degradation. In this study, the toxicity of single-shelled InZnP/Zn(Se,S) core/gradient shell and of double-shelled InZnP/Zn(Se,S)/ZnS core/shell/shell QDs was evaluated both in their pristine form and after aging in a climatic chamber, mimicking a realistic environmental weathering. We show that both pristine and aged QDs, whatever their composition, accumulate in the cytoplasm of human primary keratinocytes where they form agglomerates at the vicinity of the nucleus. Pristine QDs do not show overt toxicity to cells, while aged QDs show cytotoxicity and genotoxicity and significantly modulate the mRNA expression of proteins involved in zinc homeostasis, cell redox response, and inflammation. While the three aged QDs show similar toxicity, the toxicity of pristine gradient-shell QD is higher than that of pristine double-shell QD, confirming that adding a second shell is a promising safer-by-design strategy. Taken together, these results suggest that end-of-life degradation products from InP-based QDs are detrimental to skin cells in case of accidental exposure and that the mechanisms driving this effect are oxidative stress, inflammation, and disturbance of cell metal homeostasis, particularly Zn homeostasis. Further efforts to promote safer-by-design formulations of QDs, for instance by reducing the In and Zn content and/or implementing a more robust outer shell, are therefore warranted.

Biotransformation of Food-Grade and Nanometric TiO2 in the Oral-Gastro-Intestinal Tract: Driving Forces and Effect on the Toxicity toward Intestinal Epithelial Cells

Background: Oral exposure to titanium dioxide (TiO₂) is common since it is widely used in food and pharmaceutical products. Concern on the safety of this substance has been recently raised, due to the presence of an ultrafine fraction in food-grade TiO₂. Discrepancy exists among data reported in in vitro and in vivo studies on intestinal acute/chronic toxicity of TiO₂. This might be due to the different biological identity of TiO₂ in traditional in vitro test by respect in vivo conditions. Methods: One food-grade TiO₂ and two nanometric TiO₂ samples were treated with a simulated human digestive dystem (SHDS) in order to investigate the bio-transformation occurring to the particles once ingested in term of size distribution (Dynamic Light Scattering—DLS-, Flow Particle Imaging, Asymmetric Flow Field Flow Fractionation-AF4-) and surface modification (Electrophoretic Light Scattering—ELS-, Electron Paramagnetic Resonance Spectroscopy—EPR-). The effect of SHDS on the cyto-, genotoxicity and potential to induce oxidative stress towards human colorectal carcinoma HCT116 cells was also assessed. Results: Aggregation as a consequence of the high ionic strength of the gastric and intestinal simulated fluids was observed, together with the formation of a partially irreversible bio-corona containing phosphate ions and proteins. Such bio-corona led to a partial masking of the TiO₂ particles surface and reactivity. Pristine and treated TiO₂ nanoparticles showed comparable acute toxicity and genotoxicity toward HCT116 cells, whereas a small decrease of the induction of oxidative stress after treatment was observed. Conclusions: Overall the results underline the importance of SHDS as a tool to improve the predictive power of in vitro tests towards intestinal nanomaterial toxicity.

Toxicity to RAW264.7 Macrophages of Silica Nanoparticles and the E551 Food Additive, in Combination with Genotoxic Agents

Synthetic amorphous silica (SAS) is used in a plethora of applications and included in many daily products to which humans are exposed via inhalation, ingestion, or skin contact. This poses the question of their potential toxicity, particularly towards macrophages, which show specific sensitivity to this material. SAS represents an ideal candidate for the adsorption of environmental contaminants due to its large surface area and could consequently modulate their toxicity. In this study, we assessed the toxicity towards macrophages and intestinal epithelial cells of three SAS particles, either isolated SiO₂ nanoparticles (LS30) or SiO₂ particles composed of agglomerated-aggregates of fused primary particles, either food-grade (E551) or non-food-grade (Fumed silica). These particles were applied to cells either alone or in combination with genotoxic co-contaminants, i.e., benzo[a]pyrene (B[a]P) and methane methylsulfonate (MMS). We show that macrophages are much more sensitive to these toxic agents than a non-differenciated co-culture of Caco-2 and HT29-MTX cells, used here as a model of intestinal epithelium. Co-exposure to SiO₂ and MMS causes DNA damage in a synergistic way, which is not explained by the modulation of DNA repair protein mRNA expression. Together, this suggests that SiO₂ particles could adsorb genotoxic agents on their surface and, consequently, increase their DNA damaging potential.

TiO2 genotoxicity: An update of the results published over the last six years

TiO₂ particles are broadly used in daily products, including cosmetics for their UV-absorbing property, food for their white colouring property, water and air purification systems, self-cleaning surfaces and photoconversion electrical devices for their photocatalytic properties. The toxicity of TiO₂ nano- and microparticles has been studied for decades, and part of this investigation has been dedicated to the identification of their potential impact on DNA, i.e., their genotoxicity. This review summarizes data retrieved from their genotoxicity testing during the past 6 years, encompassing both in vitro and in vivo studies, mostly performed on lung and intestinal models. It shows that TiO₂ particles, both nano- and micro-sized, produce genotoxic damage to a variety of cell types, even at low, realistic doses.

Toward Nanotechnology-Enabled Approaches against the COVID-19 Pandemic

The COVID-19 outbreak has fueled a global demand for effective diagnosis and treatment as well as mitigation of the spread of infection, all through large-scale approaches such as specific alternative antiviral methods and classical disinfection protocols. Based on an abundance of engineered materials identifiable by their useful physicochemical properties through versatile chemical functionalization, nanotechnology offers a number of approaches to cope with this emergency. Here, through a multidisciplinary Perspective encompassing diverse fields such as virology, biology, medicine, engineering, chemistry, materials science, and computational science, we outline how nanotechnology-based strategies can support the fight against COVID-19, as well as infectious diseases in general, including future pandemics. Considering what we know so far about the life cycle of the virus, we envision key steps where nanotechnology could counter the disease. First, nanoparticles (NPs) can offer alternative methods to classical disinfection protocols used in healthcare settings, thanks to their intrinsic antipathogenic properties and/or their ability to inactivate viruses, bacteria, fungi, or yeasts either photothermally or via photocatalysis-induced reactive oxygen species (ROS) generation. Nanotechnology tools to inactivate SARS-CoV-2 in patients could also be explored. In this case, nanomaterials could be used to deliver drugs to the pulmonary system to inhibit interaction between angiotensin-converting enzyme 2 (ACE2) receptors and viral S protein. Moreover, the concept of "nanoimmunity by design" can help us to design materials for immune modulation, either stimulating or suppressing the immune response, which would find applications in the context of vaccine development for SARS-CoV-2 or in counteracting the cytokine storm, respectively. In addition to disease prevention and therapeutic potential, nanotechnology has important roles in diagnostics, with potential to support the development of simple, fast, and cost-effective nanotechnology-based assays to monitor the presence of SARS-CoV-2 and related biomarkers. In summary, nanotechnology is critical in counteracting COVID-19 and will be vital when preparing for future pandemics.

Titanium Dioxide Nanoparticles Alter the Cellular Phosphoproteome in A549 Cells

TiO₂ nanoparticles (NPs) are one of the most produced NPs worldwide and are used in many consumer products. Their impact on human health, especially through inhalation, has been studied for more than two decades. TiO₂ is known for its strong affinity towards phosphates, and consequently interaction with cellular phosphates may be one of the mechanisms driving its toxicity. In the present study, we used a phosphoproteomics approach to document the interaction of TiO₂-NP with phosphoproteins from A549 human pulmonary alveolar epithelial cells. Cells were exposed to 21 nm anatase/rutile TiO₂-NPs, then their phosphopeptides were extracted and analyzed using shotgun proteomics. By comparing the phosphoprotein content, phosphorylation status and phosphorylation sites of exposed cells with that of control cells, our results show that by affecting the phosphoproteome, TiO₂-NPs affect cellular processes such as apoptosis, linked with cell cycle and the DNA damage response, TP53 being central to these pathways. Other pathways including inflammation and molecular transport are also affected. These molecular mechanisms of TiO₂-NP toxicity have been reported previously, our study shows for the first time that they may derive from phosphoproteome modulation, which could be one of their upstream regulators.

Light sheet fluorescence microscope for microfluidic chip

We present a light sheet fluorescence microscope dedicated to image “Organ-on-chip”-like biostructures in microfluidic chip. Based on a simple design, the setup is built around the chip and its environment to allow 3D imaging inside the chip in a microfluidic laboratory. The experimental setup, its optical characterization and first volumetric images are reported.

Optimization of the harvesting and freezing conditions of human cell lines for DNA damage analysis by the alkaline comet assay

The comet assay is a commonly used method for in vitro and in vivo genotoxicity assessment. This versatile assay can be performed in a wide range of tissues and cell types. Although most of the studies use samples immediately processed after collection, frozen biological samples can also be used. The present study aimed to optimize a collection and freezing protocol to minimize the DNA damage associated with these procedures in human cell line samples for comet assay analysis. This study was conducted in glial A172 and lung alveolar epithelial A549 cells. Two cell detachment methods (mechanical vs enzymatic) and two cryoprotective media [FBS + 10% DMSO vs Cell Culture Media (CCM) + 10% DMSO] were tested, and DNA damage assessed at four time points following storage at -80 °C (one, two, four and eight weeks). In both cell lines, no differences in % tail intensity were detected between fresh and frozen cells up to eight weeks, irrespective of the harvesting method and freezing medium used. However, freshly isolated A172 cells exhibited a significant lower DNA damage when resuspended in CCM + 10% DMSO, while for A549 fresh cells the preferable harvesting method was the enzymatic one since it induced less DNA damage. Although both harvesting methods and cryoprotective media tested were found suitable, our data indicate that enzymatic harvesting and cryopreservation in CCM + 10% DMSO is a preferable method for DNA integrity preservation of human cell line samples for comet assay analysis. Our data also suggest that CCM is a preferable and cost-effective alternative to FBS in cryopreservation media. This optimized protocol allows the analysis of in vitro cell samples collected and frozen at different locations, with minimal interference on the basal DNA strand break levels in samples kept frozen up to eight weeks.

Assessment of oxidative damage induced by iron oxide nanoparticles on different nervous system cells

Iron oxide nanoparticles (ION) have received much attention for their utility in biomedical applications, such as magnetic resonance imaging, drug delivery and hyperthermia, but concerns regarding their potential harmful effects are also growing. Even though ION may induce different toxic effects in a wide variety of cell types and animal systems, there is a notable lack of toxicological data on the human nervous system, particularly important given the increasing number of applications on this specific system. An important mechanism of nanotoxicity is reactive oxygen species (ROS) generation and oxidative stress. On this basis, the main objective of this work was to assess the oxidative potential of silica-coated (S-ION) and oleic acid-coated (O-ION) ION on human SH-SY5Y neuronal and A172 glial cells. To this aim, ability of ION to generate ROS (both in the absence and presence of cells) was determined, and consequences of oxidative potential were assessed (i) on DNA by means of the 8-oxo-7,8-dihydroguanine DNA glycosylase (OGG1)-modified comet assay, and (ii) on antioxidant reserves by analyzing ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG). Conditions tested included a range of concentrations, two exposure times (3 and 24 h), and absence and presence of serum in the cell culture media. Results confirmed that, even though ION were not able to produce ROS in acellular environments, ROS formation was increased in the neuronal and glial cells by ION exposure, and was parallel to induction of oxidative DNA damage and, only in the case of neuronal cells treated with S-ION, to decreases in the GSH/GSSG ratio. Present findings suggest the production of oxidative stress as a potential action mechanism leading to the previously reported cellular effects, and indicate that ION may pose a health risk to human nervous system cells by generating oxidative stress, and thus should be used with caution.

Toxicological impact of acute exposure to E171 food additive and TiO2 nanoparticles on a co-culture of Caco-2 and HT29-MTX intestinal cells

TiO₂ particles are widely used in products for everyday consumption, such as cosmetics and food; their possible adverse effects on human health must therefore be investigated. The aim of this study was to document in vitro impact of the food additive E171, i.e. TiO₂, and of TiO₂ nanoparticles, on a co-culture of Caco-2 and HT29-MTX cells, which is an in vitro model for human intestine. Cells were exposed to TiO₂ particles three days after seeding, i.e. while they were not fully differentiated. Cell viability, reactive oxygen species (ROS) levels and DNA integrity were assessed, by MTT assay, DCFH-DA assay, alkaline and Fpg-modified comet assay and 8-oxo-dGuo measurement by HPLC-MS/MS. The mRNA expression of genes involved in ROS regulation, DNA repair via base-excision repair, and endoplasmic reticulum stress was assessed by RT-qPCR. Exposure to TiO₂ particles resulted in increased intracellular ROS levels, but did not impair cell viability and did not cause any oxidative damage to DNA. Only minor changes in mRNA expression were detected. Altogether, this shows that E171 food additive and TiO₂ nanoparticles only produce minor effects to this in vitro intestinal cell model.

Dispersion of Nanomaterials in Aqueous Media: Towards Protocol Optimization

The sonication process is commonly used for de-agglomerating and dispersing nanomaterials in aqueous based media, necessary to improve homogeneity and stability of the suspension. In this study, a systematic step-wise approach is carried out to identify optimal sonication conditions in order to achieve a stable dispersion. This approach has been adopted and shown to be suitable for several nanomaterials (cerium oxide, zinc oxide, and carbon nanotubes) dispersed in deionized (DI) water. However, with any change in either the nanomaterial type or dispersing medium, there needs to be optimization of the basic protocol by adjusting various factors such as sonication time, power, and sonicator type as well as temperature rise during the process. The approach records the dispersion process in detail. This is necessary to identify the time points as well as other above-mentioned conditions during the sonication process in which there may be undesirable changes, such as damage to the particle surface thus affecting surface properties. Our goal is to offer a harmonized approach that can control the quality of the final, produced dispersion. Such a guideline is instrumental in ensuring dispersion quality repeatability in the nanoscience community, particularly in the field of nanotoxicology.

Continuous in vitro exposure of intestinal epithelial cells to E171 food additive causes oxidative stress, inducing oxidation of DNA bases but no endoplasmic reticulum stress

The whitening and opacifying properties of titanium dioxide (TiO₂) are commonly exploited when it is used as a food additive (E171). However, the safety of this additive can be questioned as TiO₂ nanoparticles (TiO₂-NPs) have been classed at potentially toxic. This study aimed to shed some light on the mechanisms behind the potential toxicity of E171 on epithelial intestinal cells, using two in vitro models: (i) a monoculture of differentiated Caco-2 cells and (ii) a coculture of Caco-2 with HT29-MTX mucus-secreting cells. Cells were exposed to E171 and two different types of TiO₂-NPs, either acutely (6-48 h) or repeatedly (three times a week for 3 weeks). Our results confirm that E171 damaged these cells, and that the main mechanism of toxicity was oxidation effects. Responses of the two models to E171 were similar, with a moderate, but significant, accumulation of reactive oxygen species, and concomitant downregulation of the expression of the antioxidant enzymes catalase, superoxide dismutase and glutathione reductase. Oxidative damage to DNA was detected in exposed cells, proving that E171 effectively induces oxidative stress; however, no endoplasmic reticulum stress was detected. E171 effects were less intense after acute exposure compared to repeated exposure, which correlated with higher Ti accumulation. The effects were also more intense in cells exposed to E171 than in cells exposed to TiO₂-NPs. Taken together, these data show that E171 induces only moderate toxicity in epithelial intestinal cells, via oxidation.

Impact of nanoparticles on DNA repair processes: current knowledge and working hypotheses

The potential health effects of exposure to nanomaterials (NMs) is currently heavily studied. Among the most often reported impact is DNA damage, also termed genotoxicity. While several reviews relate the DNA damage induced by NMs and the techniques that can be used to prove such effects, the question of impact of NMs on DNA repair processes has never been specifically reviewed. The present review article proposes to fill this gap of knowledge by critically describing the DNA repair processes that could be affected by nanoparticle (NP) exposure, then by reporting the current state of the art on effects of NPs on DNA repair, at the level of protein function, gene induction and post-transcriptional modifications, and taking into account the advantages and limitations of the different experimental approaches. Since little is known about this impact, working hypothesis for the future are then proposed.

Long-term exposure of A549 cells to titanium dioxide nanoparticles induces DNA damage and sensitizes cells towards genotoxic agents

Titanium dioxide nanoparticles (TiO2-NPs) are one of the most produced NPs in the world. Their toxicity has been studied for a decade using acute exposure scenarios, i.e. high exposure concentrations and short exposure times. In the present study, we evaluated their genotoxic impact using long-term and low concentration exposure conditions. A549 alveolar epithelial cells were continuously exposed to 1-50 μg/mL TiO2-NPs, 86% anatase/14% rutile, 24 ± 6 nm average primary diameter, for up to two months. Their cytotoxicity, oxidative potential and intracellular accumulation were evaluated using MTT assay and reactive oxygen species measurement, transmission electron microscopy observation, micro-particle-induced X-ray emission and inductively-coupled plasma mass spectroscopy. Genotoxic impact was assessed using alkaline and Fpg-modified comet assay, immunostaining of 53BP1 foci and the cytokinesis-blocked micronucleus assay. Finally, we evaluated the impact of a subsequent exposure of these cells to the alkylating agent methyl methanesulfonate. We demonstrate that long-term exposure to TiO2-NPs does not affect cell viability but causes DNA damage, particularly oxidative damage to DNA and increased 53BP1 foci counts, correlated with increased intracellular accumulation of NPs. In addition, exposure over 2 months causes cellular responses suggestive of adaptation, characterized by decreased proliferation rate and stabilization of TiO2-NP intracellular accumulation, as well as sensitization to MMS. Taken together, these data underline the genotoxic impact and sensitization effect of long-term exposure of lung alveolar epithelial cells to low levels of TiO2-NPs.

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.

TiO(2) nanoparticles and bulk material stimulate human peripheral blood mononuclear cells

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Effects on immunobiochemical pathways of TiO₂ materials were investigated in vitro.

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TiO₂ bulk and nanomaterial stimulated neopterin production in human PBMC.

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There was no stimulatory influence of particles on tryptophan breakdown.

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At high particles concentrations, tryptophan breakdown was suppressed.

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Results suggest that the total effect of particles is even stronger pro-inflammatory.

Nanomaterials are increasingly produced and used throughout recent years. Consequently the probability of exposure to nanoparticles has risen. Because of their small 1–100 nm size, the physicochemical properties of nanomaterials may differ from standard bulk materials and may pose a threat to human health. Only little is known about the effects of nanoparticles on the human immune system. In this study, we investigated the effects of TiO₂ nanoparticles and bulk material in the in vitro model of human peripheral blood mononuclear cells (PBMC) and cytokine-induced neopterin formation and tryptophan breakdown was monitored. Both biochemical processes are closely related to the course of diseases like infections, atherogenesis and neurodegeneration. OCTi60 (25 nm diameter) TiO₂ nanoparticles and bulk material increased neopterin production in unstimulated PBMC and stimulated cells significantly, the effects were stronger for OCTi60 compared to bulk material, while P25 TiO₂ (25 nm diameter) nanoparticles had only little influence. No effect of TiO₂ nanoparticles on tryptophan breakdown was detected in unstimulated cells, whereas in stimulated cells, IDO activity and IFN-γ production were suppressed but only at the highest concentrations tested. Because neopterin was stimulated and tryptophan breakdown was suppressed in parallel, data suggests that the total effect of particles would be strongly pro-inflammatory.

Uranium interaction with two multi-resistant environmental bacteria: Cupriavidus metallidurans CH34 and Rhodopseudomonas palustris

Depending on speciation, U environmental contamination may be spread through the environment or inversely restrained to a limited area. Induction of U precipitation via biogenic or non-biogenic processes would reduce the dissemination of U contamination. To this aim U oxidation/reduction processes triggered by bacteria are presently intensively studied. Using X-ray absorption analysis, we describe in the present article the ability of Cupriavidus metallidurans CH34 and Rhodopseudomonas palustris, highly resistant to a variety of metals and metalloids or to organic pollutants, to withstand high concentrations of U and to immobilize it either through biosorption or through reduction to non-uraninite U(IV)-phosphate or U(IV)-carboxylate compounds. These bacterial strains are thus good candidates for U bioremediation strategies, particularly in the context of multi-pollutant or mixed-waste contaminations.

Accumulation, translocation and impact of TiO2 nanoparticles in wheat (Triticum aestivum spp.): influence of diameter and crystal phase

Intensive production of TiO(2) nanoparticles (TiO(2)-NPs) would lead to their release in the environment. Their ecotoxicological impact is still poorly documented, while their use in commercial goods is constantly increasing. In this study we compare root accumulation and root-to-shoot translocation in wheat of anatase and rutile TiO(2)-NPs with diameters ranging from 14 nm to 655 nm, prepared in water. NP distribution in plant tissues was mapped by synchrotron-radiation micro-X-ray fluorescence, observed by transmission electron microscopy and quantified in the different compartments of plant roots by micro-particle-induced X-ray emission. Our results provide evidence that the smallest TiO(2)-NPs accumulate in roots and distribute through whole plant tissues without dissolution or crystal phase modification. We suggest a threshold diameter, 140 nm, above which NPs are no longer accumulated in wheat roots, as well as a threshold diameter, 36 nm, above which NPs are accumulated in wheat root parenchyma but do not reach the stele and consequently do not translocate to the shoot. This accumulation does not impact wheat seed germination, biomass and transpiration. It does not induce any modification of photosynthesis nor induce oxidative stress. However exposure of wheat plantlets to the smallest NPs during the first stages of development causes an increase of root elongation. Collectively, these data suggest that only the smallest TiO(2)-NPs may be accumulated in wheat plants, although in limited amounts and that their impact is moderate.

Neurogenic inflammation in the upper digestive tract of the mule duck: effect of a chemical algogen and force-feeding

1.The objectives were to quantify the presence of neurogenic inflammation in 4 regions of the upper digestive tract of anaesthetised ducks (post-pharynx, pseudo-crop, transition between the pseudo-crop and the proventriculus, and proventriculus) after application of HCl stimulation of up to 4 M in the pseudo-crop. 2.The second objective was to quantify the presence of neurogenic inflammation in the same digestive tract regions as mentioned above during 4 feeding periods of foie gras production (rearing, preparation to force-feeding, and second and last meals of the force-feeding period). 3. Extravasation increased above a HCl stimulation threshold of 2 M. Furthermore, more extravasation was observed in the proventriculus compared to the other regions (P < 0·001). 4.Highest extravasation responses were observed in the proventriculus and the pseudo-crop at the end of the preparation period, and in the proventriculus after the second forced meal, compared with the rearing period (P < 0·01), with a return to rearing level at the end of force-feeding. 5.Such a kinetic could be indicative of a relative mildness of the irritant components associated with this feeding practice.

Titanium dioxide nanoparticles exhibit genotoxicity and impair DNA repair activity in A549 cells

Titanium dioxide nanoparticles (TiO(2)-NPs) are produced in large quantities, raising concerns about their impact for human health. The aim of this study was to deeply characterize TiO(2)-NPs genotoxic potential to lung cells, and to link genotoxicity to physicochemical characteristics, e.g., size, specific surface area, crystalline phase. A549 cells were exposed to a panel of TiO(2)-NPs with diameters ranging from 12 to 140 nm, either anatase or rutile. A set of complementary techniques (comet and micronucleus assays, gamma-H2AX immunostaining, 8-oxoGuanine analysis, H2-DCFDA, glutathione content, antioxidant enzymes activities) allowed us to demonstrate that small and spherical TiO(2)-NPs, both anatase and rutile, induce single-strand breaks and oxidative lesions to DNA, together with a general oxidative stress. Additionally we show that these NPs impair cell ability to repair DNA, by inactivation of both NER and BER pathways. This study thus confirms the genotoxic potential of TiO(2)-NPs, which may preclude their mutagenicity and carcinogenicity.

Dispersion of aeroxil P25 TiO2 nanoparticle in media of biological interest for the culture of eukaryotic cells

In this paper, results concerning the dispersion by different ways of a very common industrial titania NP (Degussa P25 produced in ton quantities). When dispersed in water, the suspensions of NP appear stable for weeks. When transferred in the cell culture medium (DMEM) or if directly dispersed in DMEM, strong evolution of size is seen as well as sedimentation. To address this problem and avoid direct aggregation, when going to DMEM, a "surfactant" relevant with biological studies (FBS) prior to transfer in DMEM (or other cell media) can be used. The main results are presented here.

Actinide speciation in relation to biological processes

In case of accidental release of radionuclides into the environment, actinides represent a severe health risk to human beings following internal contamination (inhalation, ingestion or wound). For a better understanding of the actinide behaviour in man (in term of metabolism, retention, excretion) and in specific biological systems (organs, cells or biochemical pathways), it is of prime importance to have a good knowledge of the relevant actinide solution chemistry and biochemistry, in particular of the thermodynamic constants needed for computing actinide speciation. To a large extent, speciation governs bioavailability and toxicity of elements and has a significant impact on the mechanisms by which toxics accumulate in cell compartments and organs and by which elements are transferred and transported from cell to cell. From another viewpoint, speciation is the prerequisite for the design and success of potential decorporation therapies. The purpose of this review is to present the state of the art of actinide knowledge within biological media. It is also to discuss how actinide speciation can be determined or predicted and to highlight the areas where information is lacking with the aim to encourage new research efforts.

Seleno- l -Methionine Is the Predominant Organic Form of Selenium in Cupriavidus metallidurans CH34 Exposed to Selenite or Selenate

The accumulated organic form of selenium previously detected by X-ray absorption near-edge structure (XANES) analyses in Cupriavidus metallidurans CH34 exposed to selenite or selenate was identified as seleno- l -methionine by coupling high-performance liquid chromatography to inductively coupled plasma-mass spectrometry.

Osmotic stress activated expression of an Arabidopsis plasma membrane-associated protein: sequence and predicted secondary structure

A cDNA clone At.MAMI (Arabidopsis thaliana membrane-associated mannitol-induced) was isolated from an Arabidopsis cDNA expression library by immunoselection. The cDNA was full-length (1.18 kb) with an open reading frame of 798 nucleotides encoding a 265 amino acid protein. The sequence of At.MAMI did not show any significant identity with other genes, as well as the deduced amino acid sequence with other proteins. However, prediction methods for the secondary structure of MAMI-30, together with homologous domains revealed some identity with VAP-33, a protein involved in membrane trafficking in neuronal tissues. In contrast to VAP-33, MAMI-30 did not exhibit a transmembrane domain, but positively charged loop regions could be involved in membrane anchoring. Indeed, MAMI-30 was immunodetected in purified plasma membrane from Arabidopsis cells. The gene was responsive to low turgor in Arabidopsis and its expression regulated developmentally. In addition, reduction of turgor caused a higher accumulation of mRNAs.