Publicação
In vitro combined toxicity of hexavalent chromium, nickel and benzo(a)pyrene in human lung cells
| Resumo: | Risk assessment of chemicals mainly relies on exposure to single chemicals and their hazardous effects, although the real scenario in occupational settings is more commonly characterized by exposure to chemical mixtures. Chromium (Cr), Nickel (Ni), and Polycyclic Aromatic Hydrocarbons (PAHs) are often present in occupational settings, such as aeronautic industries, where workers are exposed primarily through inhalation. Considering that those substances are recognized lung carcinogens acting mainly by genotoxic mechanisms, it is likely that interactive effects occur, indicating that the risk from occupational exposure to these chemicals should be assessed as a mixture. Such issue is being addressed in the HBM4EU Initiative, where a real scenario of occupational exposure has been studied. In order to provide support to the hazard assessment of the referred mixture, the present work aimed to evaluate the combined toxicity of Cr(VI), Ni, and benzo(a)pyrene (BaP), using a human lung cell line (A549 cells). Cytotoxicity was assessed after 24 and 48h of exposure to different concentrations of each compound and mixture of compounds. MTT assay was performed for the different mixtures and for each individual chemical and a dose-response curve was established, enabling the determination of the IC50, when possible. Genotoxicity was assessed through the micronucleus assay, after exposure for 24h, for single and mixture of compounds. The combined genotoxicity and cytotoxicity of the Cr and Ni mixture as well as that of Cr, Ni and BaP were determined comparatively to the single chemicals’ toxicity to ascertain whether additive effects or deviations from additivity towards synergism or antagonism was obtained. The results showed a high level of cytotoxicity for single Cr(VI) and single nickel; on the other hand, single BaP exposure didn’t show a significant decrease in A549 viability. Genotoxicity results for the three compounds, all showed an increase in micronuclei frequency for all tested concentrations, confirming their genotoxic potential. Binary mixtures with Cr(VI) and nickel all caused a significant decrease in cell viability for both 24 and 48h of exposure, and modelling results with the CA model showed a weak antagonism whereas with the IA model, a synergistic effect was found for lower concentrations, with an alteration to antagonism at higher concentrations. Ternary mixture with Cr(VI), nickel and BaP also caused a significant decrease in cell viability, and although no modelling was performed, an apparent antagonistic effect was observed. At a genotoxic level, both binary and ternary mixtures caused a significant increase in micronuclei frequency, and modelling results for the binary mixture showed, with the CA model, an additivity effect and with the IA model, a synergistic effect. Once again for the ternary mixture, although no modelling was performed, an apparent antagonistic effect was found. In order to consolidate the information and results presented in this work, it is necessary to explore more concentrations and different combinations. In addition, other relevant endpoints should also be explored, for example, epigenetic effects, ROS generation and effects on DNA repair. |
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| Autores principais: | Alves, Inês Arraia |
| Assunto: | Misturas Avaliação de risco Saúde ocupacional Crómio hexavalente Níquel e HAPs Teses de mestrado - 2021 |
| Ano: | 2021 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | Risk assessment of chemicals mainly relies on exposure to single chemicals and their hazardous effects, although the real scenario in occupational settings is more commonly characterized by exposure to chemical mixtures. Chromium (Cr), Nickel (Ni), and Polycyclic Aromatic Hydrocarbons (PAHs) are often present in occupational settings, such as aeronautic industries, where workers are exposed primarily through inhalation. Considering that those substances are recognized lung carcinogens acting mainly by genotoxic mechanisms, it is likely that interactive effects occur, indicating that the risk from occupational exposure to these chemicals should be assessed as a mixture. Such issue is being addressed in the HBM4EU Initiative, where a real scenario of occupational exposure has been studied. In order to provide support to the hazard assessment of the referred mixture, the present work aimed to evaluate the combined toxicity of Cr(VI), Ni, and benzo(a)pyrene (BaP), using a human lung cell line (A549 cells). Cytotoxicity was assessed after 24 and 48h of exposure to different concentrations of each compound and mixture of compounds. MTT assay was performed for the different mixtures and for each individual chemical and a dose-response curve was established, enabling the determination of the IC50, when possible. Genotoxicity was assessed through the micronucleus assay, after exposure for 24h, for single and mixture of compounds. The combined genotoxicity and cytotoxicity of the Cr and Ni mixture as well as that of Cr, Ni and BaP were determined comparatively to the single chemicals’ toxicity to ascertain whether additive effects or deviations from additivity towards synergism or antagonism was obtained. The results showed a high level of cytotoxicity for single Cr(VI) and single nickel; on the other hand, single BaP exposure didn’t show a significant decrease in A549 viability. Genotoxicity results for the three compounds, all showed an increase in micronuclei frequency for all tested concentrations, confirming their genotoxic potential. Binary mixtures with Cr(VI) and nickel all caused a significant decrease in cell viability for both 24 and 48h of exposure, and modelling results with the CA model showed a weak antagonism whereas with the IA model, a synergistic effect was found for lower concentrations, with an alteration to antagonism at higher concentrations. Ternary mixture with Cr(VI), nickel and BaP also caused a significant decrease in cell viability, and although no modelling was performed, an apparent antagonistic effect was observed. At a genotoxic level, both binary and ternary mixtures caused a significant increase in micronuclei frequency, and modelling results for the binary mixture showed, with the CA model, an additivity effect and with the IA model, a synergistic effect. Once again for the ternary mixture, although no modelling was performed, an apparent antagonistic effect was found. In order to consolidate the information and results presented in this work, it is necessary to explore more concentrations and different combinations. In addition, other relevant endpoints should also be explored, for example, epigenetic effects, ROS generation and effects on DNA repair. |
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