title: Long-term exposure of A549 cells to titanium dioxide nanoparticles induces DNA damage and sensitizes cells towards genotoxic agents.
abstract: Titanium dioxide nanoparticles (TiO2-NPs) are one of the most produced NPs in the world. Their toxicity has been studied for a decade using acute exposure scenarios, i.e. high exposure concentrations and short exposure times. In the present study, we evaluated their genotoxic impact using long-term and low concentration exposure conditions. A549 alveolar epithelial cells were continuously exposed to 1-50 μg/mL TiO2-NPs, 86% anatase/14% rutile, 24 ± 6 nm average primary diameter, for up to two months. Their cytotoxicity, oxidative potential and intracellular accumulation were evaluated using MTT assay and reactive oxygen species measurement, transmission electron microscopy observation, micro-particle-induced X-ray emission and inductively-coupled plasma mass spectroscopy. Genotoxic impact was assessed using alkaline and Fpg-modified comet assay, immunostaining of 53BP1 foci and the cytokinesis-blocked micronucleus assay. Finally, we evaluated the impact of a subsequent exposure of these cells to the alkylating agent methyl methanesulfonate. We demonstrate that long-term exposure to TiO2-NPs does not affect cell viability but causes DNA damage, particularly oxidative damage to DNA and increased 53BP1 foci counts, correlated with increased intracellular accumulation of NPs. In addition, exposure over 2 months causes cellular responses suggestive of adaptation, characterized by decreased proliferation rate and stabilization of TiO2-NP intracellular accumulation, as well as sensitization to MMS. Taken together, these data underline the genotoxic impact and sensitization effect of long-term exposure of lung alveolar epithelial cells to low levels of TiO2-NPs.
authors.affiliation: a Laboratoire Lésions Des Acides Nucléiques , Université Grenoble-Alpes, INAC-LCIB , Grenoble , France .|b Laboratoire Lésions Des Acides Nucléiques , CEA, INAC-SCIB , Grenoble , France .
authors.forename: Lucie
authors.initials: L
authors.lastname: Armand
authors.affiliation: a Laboratoire Lésions Des Acides Nucléiques , Université Grenoble-Alpes, INAC-LCIB , Grenoble , France .|b Laboratoire Lésions Des Acides Nucléiques , CEA, INAC-SCIB , Grenoble , France .
authors.forename: Adeline
authors.initials: A
authors.lastname: Tarantini
authors.affiliation: a Laboratoire Lésions Des Acides Nucléiques , Université Grenoble-Alpes, INAC-LCIB , Grenoble , France .|b Laboratoire Lésions Des Acides Nucléiques , CEA, INAC-SCIB , Grenoble , France .
authors.forename: David
authors.initials: D
authors.lastname: Beal
authors.affiliation: a Laboratoire Lésions Des Acides Nucléiques , Université Grenoble-Alpes, INAC-LCIB , Grenoble , France .|b Laboratoire Lésions Des Acides Nucléiques , CEA, INAC-SCIB , Grenoble , France .
authors.forename: Mathilde
authors.initials: M
authors.lastname: Biola-Clier
authors.affiliation: a Laboratoire Lésions Des Acides Nucléiques , Université Grenoble-Alpes, INAC-LCIB , Grenoble , France .|b Laboratoire Lésions Des Acides Nucléiques , CEA, INAC-SCIB , Grenoble , France .
authors.forename: Laure
authors.initials: L
authors.lastname: Bobyk
authors.affiliation: c CENBG, Université Bordeaux 1, IN2P3, UMR5797 , Gradignan Cedex , France .
authors.forename: Sephanie
authors.initials: S
authors.lastname: Sorieul
authors.affiliation: d Grenoble Institut Des Neurosciences, Université Grenoble Alpes , Grenoble , France .|e INSERM U 836 , Grenoble , France .
authors.forename: Karin
authors.initials: K
authors.lastname: Pernet-Gallay
authors.affiliation: f Medical Biology Laboratory (LBM), Université Grenoble-Alpes, CEA, Nanosafety Platform , Grenoble , France .
authors.forename: Caroline
authors.initials: C
authors.lastname: Marie-Desvergne
authors.affiliation: g School of Geography Earth and Environmental Sciences, University of Birmingham , Edgbaston , Birmingham , UK , and.
authors.forename: Iseult
authors.initials: I
authors.lastname: Lynch
authors.affiliation: h UMR3685 CEA-CNRS, NIMBE, LEDNA, CEA Saclay , Gif Sur Yvette , France.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Herlin-Boime
authors.affiliation: a Laboratoire Lésions Des Acides Nucléiques , Université Grenoble-Alpes, INAC-LCIB , Grenoble , France .|b Laboratoire Lésions Des Acides Nucléiques , CEA, INAC-SCIB , Grenoble , France .
authors.forename: Marie
authors.initials: M
authors.lastname: Carriere
mesh_terms: D000072283:A549 Cells; D056809:Alveolar Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D018929:Cell Culture Techniques; D002470:Cell Survival / Q000187:drug effects; D020552:Comet Assay; D004249:DNA Damage; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015162:Micronucleus Tests; D046529:Microscopy, Electron, Transmission; D009153:Mutagens / Q000737:chemistry / Q000633:toxicity*; D053758:Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D010316:Particle Size; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors; D014025:Titanium / Q000737:chemistry / Q000633:toxicity*
chemical_list: D009153:Mutagens; D017382:Reactive Oxygen Species; C009495:titanium dioxide; D014025:Titanium
keywords: Genotoxicity; TiO2; mechanistic toxicology; nanoparticles; toxicity