Génotoxicité et impact de nanoparticules de dioxyde de titane sur la réparation de l’ADN dans des cellules alvéolaires pulmonaires

Mathilde Biola-Clier 1
1 LAN - Laboratoire Lésions des Acides Nucléiques
SCIB - UMR E3 - Service de Chimie Inorganique et Biologique : DSM/INAC/SCIB
Abstract : Titanium dioxide (TiO2) belongs to the top nanoparticles (NPs) most produced worldwide. This raises the question of their impact on human health, especially through inhalation, which is the main exposure route in occupational settings. It was previously shown in vitro that these NPs induce DNA damage and impair DNA repair activity. The aim here is to study the underlying toxicity mechanisms, in human A549 epithelial alveolar cells exposed to 1-100 µg/ml TiO2 NPs during 4-48 h. The expression of 40 genes and 6 proteins involved in DNA repair was investigated by RT-qPCR and western-blotting. The impact of TiO2 NPs on upstream regulators such as the methylation rate of some corresponding gene promoters, proteasome activity and cellular signaling through phosphorylation was assayed as well. Moreover cyto-/geno-toxicity and DNA repair gene expression patterns were compared with those of BEAS-2B bronchial epithelial cells. Results show a global down-regulation of genes and proteins in all DNA repair pathways. This could be partly explained by the down-regulation of transcriptional regulators and increased gene promoter methylation and caspase-like proteasome activity. TiO2 NPs also scramble the phosphoproteome. While invisible on a global scale, this dysregulation affects numerous proteins involved in diverse cellular processes, which reflect the toxicity pathways reported for these NPs. Although cell proliferation is unaffected, a significant impact is observed on cell cycle, as well as on a few proteins involved in DNA repair. Finally cyto-/geno-toxicity and DNA repair gene expression profiles are similar in both A549 and BEAS-2B cells, thereby strengthening the relevance of using any of these cell lines in nanomaterial genotoxicity studies. On the whole these data bring novel insights into TiO2-NP toxicity mechanisms, which could especially explain the previously observed impairment of DNA repair activity.
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Submitted on : Tuesday, May 24, 2016 - 9:42:08 AM
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Mathilde Biola-Clier. Génotoxicité et impact de nanoparticules de dioxyde de titane sur la réparation de l’ADN dans des cellules alvéolaires pulmonaires. Biochimie, Biologie Moléculaire. Université Grenoble Alpes, 2016. Français. ⟨NNT : 2016GREAV004⟩. ⟨tel-01320524⟩

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