Browsing by Issue Date, starting with "2019-09-25"
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- Ingested nanomaterials: effects of titanium dioxide in human cellsPublication . Gramacho, Ana Catarina; Silva, Maria João; Louro, HenriquetaNowadays, the consumer products containing nanomaterials (NMs) are numerous. Among these, titanium dioxide nanomaterials (TiO2) are the most frequently applied, used as food additive, pharmaceuticals, toothpastes and many more. The wide commercialization of consumer products containing TiO2 contributes to a substantial increase of human exposure to this compound, which is worrying for public health, since the existent studies generated contradictory results about TiO2 safety. The fact that NMs are dependent of the context (surrounding matrix) can contribute to explain the contradictory results reported in the literature. Furthermore, it has been hypothesized that NMs physicochemical properties may define bio-nano interactions, which suggest that NMs with the same chemistry but with different shape, diameter, length, surface charge or functionalization may lead to different toxicities (Louro et al., 2019). This work aimed to assess whether the secondary physicochemical characteristics of three different TiO2, i.e., the characteristics after the digestion process, produce different biological effects in intestinal cells. The three NMs were obtained from the Joint Research Centre, Ispra, Italy (NM-102, NM-103 and NM-105), and display different charge, size and crystal structure, coated and uncoated, as characterized by the producer (Rasmussen et al., 2014). An in vitro digestion process was used to mimic human digestion (Brodkorb et al., 2019) and the resulting product was used for cytotoxicity assessment in a human intestinal cell line (Caco-2), in comparison to undigested NMs. In addition, cellular uptake was investigated using confocal microscopy. Preliminary results did not evidence a differential biological effect between the three NMs. Following 24h of exposure of Caco-2 cells, all the digested NMs behaved similarly at the concentrations tested (0.14 – 14.3 µg/ml) showing no cytotoxic effects. Likewise, no cytotoxic effects were observed upon exposure to undigested NMs. However, the results showed the nuclear localization of one NM, NM-102, suggesting that it may interact with the genome in cells exposed to this TiO2. Ongoing studies will confirm the subcellular localization of the NMs in exposed intestinal cells and will investigate their genotoxic effects in relation with the secondary properties.
- Exploring the toxicity of cellulose nanofibrils in a lung epithelial cell linePublication . Teixeira, Sara; Lourenço, Ana Filipa; Ventura, Célia; Louro, Henriqueta; Ferreira, Paulo; Silva, Maria JoãoNanotechnologies and nanomaterials (NMs) applications have been growing in recent years, bringing benefits to society but raising also some concerns about their safety to human health. Cellulose is a natural material that fits the global trend of sustainability: ecological, low cost, abundant and renewable nature. In particular, cellulose nanofibrils (CNF)1 are forest-derived products with advantageous mechanical, optical and rheological properties, assuming a high industrial potential, e.g., in paper, food, pharmaceutical and biomedical industries. With the innovative applications expanding, CNF synthesis and production has increasing, leading to concerns about occupational exposure, particularly by inhalation, or consumers exposure. The toxicity studies of other NMs, like MWCNT, have had a major impact on the understanding of the nanofibres health effects on humans. MWCNTs have been reported to cause adverse effects in vitro and in vivo, such as DNA damage and oxidative stress2. Because CNF show a high resemblance in terms of aspect ratio to MWCNT, our main focus is to identify if some of the CNF synthesized have a genotoxic or carcinogenic potential. This study aims to assess the safety of two types of CNF produced with different pre-treatments (TEMPO-mediated oxidation and enzymatic hydrolysis) of an industrial bleached Eucalyptus globulus kraft pulp, through the characterization of its cytotoxicity and genotoxicity in human cells. The CNF cytotoxicity was assessed using lung epithelial alveolar (A549) cells by two methodologies, the MTT and the clonogenic assay, whereas the genotoxicity was assessed by the cytokinesis-block micronucleus assay. Dose-range finding experiments were performed using the MTT (24h, 48h and 72h exposure) and the clonogenic (8 days exposure) assays, which revealed that both CNF were not cytotoxic at concentrations between 3,125 and 100 μg/ml. On the contrary, both CNFs were able to increase cell viability at the highest concentrations tested (50 and 100 μg/ml). This effect had been previously observed in the same cell line exposed to CNF produced by TEMPO-mediated oxidation, but at the lowest concentration level3. The potential of the CNF to induce chromosomal alterations, either chromosome breaks or loss is being analysed through the micronucleus assay and the results will be presented. Overall, this study is expected to uncover potential adverse outcomes of CNF to human health, in order to promote the design of safer CNF and CNF-based products that will allow a more sustainable and responsible industrial development. References: 1) Gamelas, J., Pedrosa, J., Lourenço, A., Mutjé, P., González, I., Chinga-Carrasco, G., Singh, G. and Ferreira, P. (2015). On the morphology of cellulose nanofibrils obtained by TEMPO-mediated oxidation and mechanical treatment. Micron, 72, 28-33. 2) Louro, H., Pinhão, M., Santos, J., Tavares, A., Vital, N. and Silva, M. (2016). Evaluation of the cytotoxic and genotoxic effects of benchmark multi-walled carbon nanotubes in relation to their physicochemical properties. Toxicology Letters, 262, 123-134. 3) Ventura, C., Lourenço, A., Sousa-Uva, A., Ferreira, P. and Silva, M. (2018). Evaluating the genotoxicity of cellulose nanofibrils in a co-culture of human lung epithelial cells and monocyte-derived macrophages. Toxicology Letters, 291, 173-183.
- Paralytic shellfish poisoning due to ingestion of contaminated mussels: a 2018 case report in Caparica (Portugal)Publication . Lopes de Carvalho, I.; Pelerito, A.; Ribeiro, I.; Cordeiro, R.; Núncio, M.S.; Vale, P.In Portugal, the potent paralytic shellfish toxins (PSTs) have appeared irregularly since the onset of a national monitoring program for marine biotoxins in 1986. In years where high contamination levels were attained in bivalves, sporadic cases of human poisonings have been recorded, as in 1994 and 2007. The reappearance of high contamination levels led to the appearance of new cases during the autumn of 2018. This study details toxin ingestion, symptomatology and toxin elimination and metabolization in the fluids of two patients, who ingested mussels from the Portuguese southwest coast and required hospitalization due to the severity of symptoms. Toxin elimination was confirmed by ELISA in plasma and urine samples. In mussel samples, the toxin profile obtained by HPLC-FLD displayed a wide diversity of toxins, typical of Gymnodinum catenatum ingestion. However, in the urine samples, the toxin profile was reduced to B1 and dcSTX. Abundant compounds in mussels having an O- sulphate at C11, such as C1þ2 and dcGTX2þ3, were absent in urine. In plasma, PSTs were not detected by HPLC- FLD. Calculated toxin ingestion, resulting from consumption of an estimated 200-g portion, was in the range of 104–120 μg STX eq./kg b. w.
- Occupational exposure to hexavalent chromium: biomarkers of genotoxicity in human peripheral bloodPublication . Afonso, Catarina; Gomes, Bruno Costa; Louro, Henriqueta; Nogueira, Ana; Pinhal, Hermínia; Reis, Susana; Ventura, Célia; Ladeira, Carina; Ribeiro, Edna; Santonen, Tiina; Viegas, Susana; Silva, Maria JoãoThe hexavalent chromium [Cr(VI)] is a human carcinogen, which is still authorized for use in several industrial settings because it has been difficult to replace. This was the reasoning to select it as a priority chemical by the European Human Biomonitoring Initiative (HBM4EU, https://www.hbm4eu.eu/), which aims to bridge chemicals human exposure to their possible impact on health. For that purpose, not only exposure needs to be assessed but also early effect biomarkers are valuable to reflect health outcomes. The cytokinesis-block micronucleus (CBMN) assay in peripheral blood lymphocytes (PBLs) is one of the most widely used effect biomarker for measuring chromosome alterations in human cells. Since it represents a measure of both chromosome breakage and loss, an increased frequency of micronucleated cells (MNC) can reflect the effect from exposure to genotoxic agents. Moreover, there is evidence that the micronucleus (MN) frequency in PBLs is predictive of cancer risk. As part of an European multi-centre occupational study, 50 Portuguese workers exposed on a daily basis to Cr(VI) and 27 healthy controls non-exposed to Cr(VI) or other chemicals were studied. The present work intended to assess, in a more detailed manner, the early effects in a subgroup of workers (n=6) that use daily paints with Cr(VI), comparatively to that of a control group matched for age, gender and smoking habits. All participants accepted to participate by signing an informed consent previously to the blood withdrawal. An individual questionnaire to collect contextual information, e.g. personal information, lifestyle habits (smoking habits, alcohol consumption, diet), and health status was filled. Personal air samples were collected in order to assess occupational exposure to Cr(VI) soluble and insoluble compounds. Following blood culture, lymphocytes harvesting and staining using standardized methods, MNC were scored in 2000 PBL per individual. The frequencies of MNC obtained for the exposed and control groups were compared using Fisher’s exact test. Results from personal air sampling are still under evaluation. A significantly increased frequency of MNC was observed in PBLs of the 6 workers under study, comparatively to the matched controls (p < 0.001, Fisher’s exact test). These results are in line with the preliminary data obtained for the overall exposed group vs controls. The present results suggest that the frequency of micronuclei in PBLs is a reliable early effect biomarker in the case of occupational exposure to Cr(VI). Moreover, the findings also suggest a potential health risk for this group of workers. These results should promote the investment in new risk management measures and the effective application of the ones already in place, such as adequate local exhaust ventilation and a more frequent use of personal protective equipment. Additional work, considering the overall exposed group, will be developed aiming to clarify if the obtained results are due to the single exposure to Cr(VI) or to the co-exposure to several other chemicals commonly present in this type of occupational setting.