Simultaneous Quantification and Visualization of Titanium Dioxide Nanomaterial Uptake at the Single Cell Level in an In Vitro Model of the Human Small Intestine

International audienceUseful properties render titanium dioxide nanomaterials (NMs) to be one of the most commonly used NMs worldwide. TiO2 powder is used as food additives (E171), which may contain up to 36% nanoparticles. Consequently, humans could be exposed to comparatively high amounts of NMs that may induce adverse effects of chronic exposure conditions. Visualization and quantification of cellular NM uptake as well as their interactions with biomolecules within cells are key issues regarding risk assessment. Advanced quantitative imaging tools for NM detection within biological environments are therefore required. A combination of the label-free spatially resolved dosimetric tools, microresolved particle induced X-ray emission and Rutherford backscattering, together with high resolution imaging techniques, such as time-of-flight secondary ion mass spectrometry and transmission electron microscopy, are applied to visualize the cellular translocation pattern of TiO2 NMs and to quantify the NM-load, cellular major, and trace elements in differentiated Caco-2 cells as a function of their surface properties at the single cell level. Internalized NMs are not only able to impair the cellular homeostasis by themselves, but also to induce an intracellular redistribution of metabolically relevant elements such as phosphorus, sulfur, iron, and copper

Climate Adaptation of Rubble Mound Breakwaters: A study to the accuracy of overtopping formulas for combination of solutions

Rubble mound structures are often constructed to prevent severe wave damage to ships. By constructing the crest at a certain level, the waves are reduced such that safety is ensured. However, a large increase in sea level rise is expected in the next century due to climate change. Because of this, multiple adaptations might be necessary to meet the required lifetime of a rubble mound structure. In current guidelines, the influence of these adaptations is already included. However, for a combination of solutions the empirical equations are not always accurate enough (van Gent, 2019). Accurate guidelines are necessary to correctly predict the overtopping rates for a combination of solutions. In this research, the accuracy of current guidelines is investigated.The research performed in this thesis is divided into two parts. First, multiple solutions are derived to adapt a breakwater and ensure safety for a rising sea level based on existing empirical equations. Safety is ensured if the mean overtopping rate remains less than 50 l/s/m. Beyond this point, the ships behind the structure might become prone to large wave attacks. Secondly, the accuracy of current guidelines (i.e. the empirical overtopping equations) is tested in an OpenFOAM model. OpenFOAM is a so-called open-source Computational Fluid Dynamics (CFD) software that can solve complex fluid flows.Several solutions are possible to ensure safety against severe wave overtopping. The four solutions applied in this thesis are the addition of a berm, the addition of a crest wall, an increased foreshore and the implementation of a low-crested structure. By combining these solutions, the overtopping rate remains below the maximum of 50 l/s/m. The combination of solutions forms a path, all paths together form a pathway. The adaptation pathways are a guideline for the moment in time at which a certain solution should be implemented. Therefore, a structure is not unnecessarily expensive and can be managed easily. The paths are rated based on the implementation costs of the combination of solutions.In total two empirical equations are applied to derive an adaptation pathway. The first pathway is based on the overtopping equation proposed by the TAW (2002). The TAW is a Dutch advisory committee on flood defences. Based on the applied theory, the economically most attractive solution consists of a low-crested structure, a foreshore and a berm. As this equation does not account for the influence of a berm in non-breaking waves, an adapted TAW equation is applied as well. The adapted equation was proposed by Krom (2012) and includes the influence of a berm. Based on the adapted equation, the economically most attractive solution consists of a foreshore, a crest wall and a berm. Once the economically most attractive solution is derived, the accuracy of current guidelines is reviewed in a phase-resolving model. It is found that, there is a large discrepancy between the results calculated with the empirical equations and the results from the model. As no physical data is applied in this research it is hard to interpret and analyze the exact numbers. Therefore, the relative effect of an adaptation is compared. It is found that in contrast to the TAW overtopping equation for non-breaking waves, a berm decreases the overtopping rate by at least 30% for the case study applied. Furthermore, the current method to account for a crest wall proposed by the TAW overestimates the reduction (73% compared to 40% in OpenFOAM). Finally, it is concluded that the addition of a low-crested structure decreases the overtopping rate by a larger value than based on the applied guidelines (74% in OpenFOAM compared to 35% in theory).Based on the performed research a realistic combination of the adaptation measures consists of a combination of a berm, a crest wall and a shallow foreshore. Therefore, it is advised to focus further research on the combination of these measures. It is necessary to improve the guidelines for combinations of these adaptation measures since the existing ones seem to be either incorrect (TAW, 2002) or require a better validation (Krom, 2012).Civil Engineering | Hydraulic Engineerin

An Evaluation of the Cytotoxic and Genotoxic Effects of the Marine Toxin C17-SAMT in Human TK6 and HepaRG Cell Lines

This study investigates the genotoxicity and cytotoxicity of C17-sphinganine analog mycotoxin (C17-SAMT) using in vitro assays. C17-SAMT was previously identified as the cause of unusual toxicity in cultured mussels from the Bizerte Lagoon in northern Tunisia. While a previous in vivo genotoxicity study was inconclusive, in vitro results demonstrated that C17-SAMT induced an increase in micronucleus formation in human lymphoblastoid TK6 cells at concentrations of 0.87 µM and 1.74 µM. In addition, multiparametric cytotoxicity assays were performed in the human hepatoma HepaRG cell line, which showed that C17-SAMT induced mitochondrial dysfunction, decreased cellular ATP levels, and altered the expression of various proteins, including superoxide dismutase SOD2, heme oxygenase HO-1, and NF-κB. These results suggest that C17-SAMT is mutagenic in vitro and can induce mitochondrial dysfunction in HepaRG cells. However, the exact mode of action of this toxin requires further investigation. Overall, this study highlights the potential toxicity of C17-SAMT and the need for further research to better understand its effects

Genotoxic effects of food contact recycled paperboard extracts on two human hepatic cell lines.

IF 2.047International audienceFood contact paperboards may be a potential source of food contamination as they can release chemicals (intentionally added or not), especially recycled paperboards. In this study, we assessed the in vitro genotoxicity of food contact paperboard samples from a manufacturer, collected at the beginning and at the end of a recycling production chain. Samples were extracted in water to mimic a wet food contact. Different genotoxic endpoints were evaluated in two human hepatic cell lines (HepG2 and HepaRG) using bioassays: γH2AX and p53 activation, primary DNA damage with the comet assay and micronucleus formation. We found that the samples from the beginning and the end of the production chain induced, with the same potency, γH2AX and p53-ser15 activation and DNA damage with the comet assay. The micronucleus assay was negative with the paperboard extract from the beginning of the chain, whereas positive data were observed for the end paperboard extract. Our results indicate that samples from recycled food contact paperboard can induce in vitro genotoxic effects in our experimental conditions

Genotoxicity of Aluminum and Aluminum Oxide Nanomaterials in Rats Following Oral Exposure

Due to several gaps remaining in the toxicological evaluation of nanomaterials (NMs), consumers and public health agencies have shown increasing concern for human health protection. In addition to aluminum (Al) microparticles, Al-containing nanomaterials (Al NMs) have been applied by food industry as additives and contact materials. Due to the limited amount of literature on the toxicity of Al NMs, this study aimed to evaluate the in vivo genotoxic potential of Al0 and Al2O3 NMs after acute oral exposure. Male Sprague-Dawley rats were administered three successive gavages at 6, 12.5 and 25 mg/kg bw. A comparison with AlCl3 was done in order to assess the potential effect of dissolution into Al ions. Both DNA strand breaks and oxidative DNA damage were investigated in six organs/tissues (duodenum, liver, kidney, spleen, blood and bone marrow) with the alkaline and the Fpg-modified comet assays. Concomitantly, chromosomal damage was investigated in bone marrow and colon with the micronucleus assay. The comet assay only showed DNA damage with Al2O3 NMs in bone marrow (BM), while AlCl3 induced slight but non-significant oxidative DNA damage in blood. No increase of chromosomal mutations was observed after treatment with the two Al MNs either in the BM or in the colons of rats

Toxicity, genotoxicity and proinflammatory effects of amorphous nanosilica in the human intestinal Caco-2 cell line

International audienceSilica (SiO2) in its nanosized form is now used in food applications although the potential risks for human health need to be evaluated in further detail. In the current study, the uptake of 15 and 55 nm colloidal SiO2 NPs in the human intestinal Caco-2 cell line was investigated by transmission electron microscopy. The ability of these NPs to induce cytotoxicity (XTT viability test), genotoxicity (γH2Ax and micronucleus assay), apoptosis (caspase 3), oxidative stress (oxidation of 2,7-dichlorodihydrofluorescein diacetate probe) and proinflammatory effects (interleukin IL-8 secretion) was evaluated. Quartz DQ12 was used as particle control. XTT and cytokinesis-block micronucleus assays revealed size- and concentration-dependent effects on cell death and chromosome damage following exposure to SiO2 nanoparticles, concomitantly with generation of reactive oxygen species (ROS), SiO2-15 nm particles being the most potent. In the same way, an increased IL-8 secretion was only observed with SiO2-15 nm at the highest tested dose (32 μg/ml). TEM images showed that both NPs were localized within the cytoplasm but did not enter the nucleus. SiO2-15 nm, and to a lower extent SiO2-55 nm, exerted toxic effects in Caco-2 cells. The observed genotoxic effects of these NPs are likely to be mediated through oxidative stress rather than a direct interaction with the DNA. Altogether, our results indicate that exposure to SiO2 NPs may induce potential adverse effects on the intestinal epithelium in vivo

A specific programme of gene transcription in male germ cells

The differentiation of male germ cell requires spermatogenic stage and cell-specific gene expression that is achieved by unique chromatin remodelling, transcriptional control, and the expression of testis-specific genes or isoforms. Specialized transcription complexes that coordinate the differentiation programme of spermatogenesis have been found in germ cells, which display specific differences in the components of the general transcription machinery. The TATA-binding (TBP) protein family and its associated co-factors, for example, show upregulated expression in testis. In this physiological context, transcriptional control mediated by the activator CREM represents an established paradigm. In somatic cells, activation by CREM requires its phosphorylation at a unique regulatory site (Ser117) and subsequent interaction with the ubiquitous coactivator CBP. In testis, CREM transcriptional activity is controlled through interaction with a tissue-specific partner, ACT, which confers a powerful, phosphorylation-independent activation capacity. The function of ACT is regulated by a testis-specific kinesin, KIF17b. This study discusses some aspects of the testis-specific transcription machinery, the function of which is essential for the process of spermatogenesis

Lysophosphatidylcholine-DHA Specifically Induces Cytotoxic Effects of the MDA-MB-231 Human Breast Cancer Cell Line <i>In Vitro</i>—Comparative Effects with Other Lipids Containing DHA

Docosahexaenoic acid (DHA, C22:6 ω-3) is a dietary polyunsaturated fatty acid that has an important role in human health. Epidemiological studies linked a high intake of DHA to a reduced risk of certain cancers. Recently, attention focused on how the lipid carrier in which DHA is delivered, i.e., esterified on acylglycerols, phospholipids, or free, affects its biological effects. However, studies comparing the effects of these different forms for DHA supply to cancer cells in vitro are limited. In this study, the effect of free DHA and five lipids carrying one to three DHA chains (LPC-DHA, PC-DHA, MAG-DHA, DAG-DHA and TAG-DHA) on the viability of the MDA-MB-231 breast cancer cell line was compared. Our results revealed a strong structure–function relationship of DHA-carrying lipids on the viability of MDA-MB-231 cells. Glycerophosphocholine-based lipids are the most effective DHA carriers in reducing the viability of MDA-MB-231 cells, with LPC-DHA being more effective (IC50 = 23.7 µM) than PC-DHA (IC50 = 67 µM). The other tested lipids are less toxic (MAG-DHA, free DHA) or even not toxic (DAG-DHA, TAG-DHA) under our conditions. Investigating the mechanism of cell death induced by LPC-DHA revealed increased oxidative stress and membrane cell damage