Browsing by Issue Date, starting with "2023-12-01"
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- Epigenomics as a novel approach to explore the toxic effects of nanomaterialsPublication . Ventura, Célia; Vieira, Luís; Valente, Ana; Fernandes, Camila; Silva, Catarina; Louro, Henriqueta; Ferreira, Paulo J.T.; Silva, Maria JoãoIn recent years, there has been a huge development of innovative engineered nanomaterials with potential use in industrial and biomedical applications. This increased widespread use raised concerns that nanomaterials may elicit human adverse health effects through occupational, environmental or consumer exposure. Many toxicity studies, mainly in vitro, have showed that some nanomaterials, such as carbon nanotubes or titanium dioxide nanoparticles (TiO 2 NP), may cause genotoxicity, inflammation, and associated adverse health effects. Nevertheless, few studies have focused on the nanomaterials effect s on the epigenome, namely, modifications of histone tails, microRNA expression or DNA methylation. Here we wil l present two “omics” studies based on next generation sequencing , one focusing on the effect of three nanocellulose s derived from Eucaliptus globulus kraft pulp on the microRNA expression of BEAS 2B, and an other one focusing on the effect of three types of TiO 2 NP on the DNA methylation of Caco 2 cells. Regarding the former 24h exposure to fibrillar micro/nanocellulose s did not induced significant (FDR ≤ 0.05) differentially expressed microRNAs, as compared to non exposed cells. By contrast, the crystalline nanocelul l ose induced the over and under expression of 22 and 30 microRNAs, respectively. These microRNAs can be f urther explored as potential biomarkers for human biomonitoring and co ntribute to elucidate the mechanisms of action of crystalline nanocellulose. As to the genome wide methylation study Reduced Representative Bisulfite Sequencing allowed the identification of significant ( p ≤ 0.05) differential methylation of 92, 70, and 88 gene sequences for the anatase, rutile and brookite phase TiO 2 NP exposures, respectively. Functional pathway analysis of these methylation changes showed that all TiO 2 NP may affect cell proliferation, differentiation, and survival, and suggested different molecular mechanisms of action for each type of TiO 2 NP. In conclusion, epigenomics revealed to be a powerful tool to understand the key molecular events underlying nanomaterials effects.
- Global DNA methylation and Reactive Oxygen Species assessment after in vitro exposure to novel cellulose nanomaterials on intestinal cellsPublication . Vital, Nádia; Ventura, Célia; Kranendonk, M.; Silva, Maria João; Louro, HenriquetaInnovative cellulose nanomaterials (CNMs) find applications in multiple food-related products. However, it is recognized that nanomaterials (NMs) may cause adverse effects frequently by biological mechanisms that include production of intrinsic reactive oxygen species (ROS), or epigenetic alterations, by changes in gene expression through alterations in DNA methylation. To contribute to the safety assessment of two types of micro/nanofibrillated celluloses (CMF/CNFs) derived from industrial Eucalyptus globulus kraft, intracellular ROS levels and global DNA methylation patterns were evaluated using human intestinal cell models exposed to these CNMs. A harmonized protocol for in vitro simulation of human digestion was applied to incorporate the effect of potential changes in the physicochemical properties of CNMs due to the digestion process. After exposure of intestinal cells to digested and undigested CNMs samples (concentrations from 3.1 to 200 μg/mL, 3h and 24h), ROS levels were determined using the 2,7-dichlorofluorescein diacetate probe and fluorescence detection. The global DNA methylation was assessed after 24h exposure, using the methylated DNA Quantification Kit(colorimetric, Abcam) to quantify the levels of methylated cytosines (5-methylcytosine) in CpG dinucleotides. No increased ROS were observed after exposure to CNMs with and without digestion. Conversely, the preliminary results showed significant increased methylation of DNA after exposure to the CMF, without digestion, as compared to the negative control. No effect could be observed for digested sample, possibly due to the high background of the digestion product per se. Our preliminary findings seem to suggest the occurrence of biological effects of CNMs in intestinal cells that require further investigation, as may lead to a toxic impact on gastrointestinal cells, of concern for human health.
- Multidrug-resistant Escherichia coli and Salmonella spp. in pigs slaughtered for human consumption, a potential source for Humans?Publication . Pista, Angela; Silveira, Leonor; Costa, Sara; Rosa, Rute; Gonçalves, Carlota; Alves, Margarida; Belas, Adriana; Santos, Isabel; Lima, Ana; Pedroso, Laurentina; Gomes, João Paulo; Ramos, Sónia; Nunes, AlexandraObjective: To assess the role of pig reservoir as potential transmission vehicle of Salmonella spp. and E. coli to humans, in order to understand the epidemiology and population structure of these zoonotic agents in Portugal.
- Multiparametric in vitro genotoxicity assessment of different variants of amorphous silica nanomaterials in rat alveolar epithelial cellsPublication . Brandão, Fátima; Costa, Carla; Bessa, Maria João; Valdiglesias, Vanessa; Hellack, Bryan; Haase, Andrea; Fraga, Sónia; Teixeira, João PauloThe hazard posed to human health by inhaled amorphous silica nanomaterials (aSiO2 NM) remains uncertain. Herein, we assessed the cyto- and genotoxicity of aSiO2 NM variants covering different sizes (7, 15, and 40 nm) and surface modifications (unmodified, phosphonate-, amino- and trimethylsilyl-modified) on rat alveolar epithelial (RLE-6TN) cells. Cytotoxicity was evaluated at 24 h after exposure to the aSiO2 NM variants by the lactate dehydrogenase (LDH) release and WST-1 reduction assays, while genotoxicity was assessed using different endpoints: DNA damage (single- and double-strand breaks [SSB and DSB]) by the comet assay for all aSiO2 NM variants; cell cycle progression and γ-H2AX levels (DSB) by flow cytometry for those variants that presented higher cytotoxic and DNA damaging potential. The variants with higher surface area demonstrated a higher cytotoxic potential (SiO2_7, SiO2_15_Unmod, SiO2_15_Amino, and SiO2_15_Phospho). SiO2_40 was the only variant that induced significant DNA damage on RLE-6TN cells. On the other hand, all tested variants (SiO2_7, SiO2_15_Unmod, SiO2_15_Amino, and SiO2_40) significantly increased total γ-H2AX levels. At high concentrations (28 µg/cm2), a decrease in G0/G1 subpopulation was accompanied by a significant increase in S and G2/M sub-populations after exposure to all tested materials except for SiO2_40 which did not affect cell cycle progression. Based on the obtained data, the tested variants can be ranked for its genotoxic DNA damage potential as follows: SiO2_7 = SiO2_40 = SiO2_15_Unmod > SiO2_15_Amino. Our study supports the usefulness of multiparametric approaches to improve the understanding on NM mechanisms of action and hazard prediction.