Titanium dioxide (TiO2) nanoparticles (NPs) are manufactured worldwide in large quantities for use in a wide range of applications including pigment and cosmetic manufacturing. Although TiO2 is chemically inert, TiO2 NPs can cause negative health effects, like respiratory tract cancer in rats. However, the mechanisms involved in TiO2-induced genotoxicity and carcinogenicity have not been clearly defined and are poorly studied in vivo. The present study investigates TiO2 NP-induced genotoxicity, oxidative DNA damage and inflammation in a mice model. We treated wild type mice with TiO2 NPs in drinking water and determined the extent of DNA damage using the comet assay, the micronuclei assay, the γ-H2AX immuno-staining assay and by measuring 8-hydroxy-2′-deoxyguanosine (8-OHdG) levels and, as genetic instability end point, DNA deletions. We also determined mRNA levels of inflammatory cytokines in the peripheral blood. Our results show that TiO2 NPs induced 8-OHdG, γ-H2AX foci, micronuclei and DNA deletions. The formation of γ-H2AX foci, indicative of DNA double strand breaks, was the most sensitive parameter. Inflammation was also present as characterized by a moderate inflammatory response. Together these results describe the first comprehensive study of TiO2 NP induced genotoxicity in vivo in mice, possibly caused by a secondary genotoxic mechanism associated with inflammation and/or oxidative stress. Given the growing use of TiO2 NPs, these findings raise concern about potential health hazards associated with TiO2 NP exposure.

MSH2 is a central component of the mismatch repair pathway that targets mismatches arising during DNA replication, homologous recombination (HR) and in response to genotoxic stresses. Here, we describe the function of MSH2 in the moss Physcomitrella patens, as deciphered by the analysis of loss of function mutants. Ppmsh2 mutants display pleiotropic growth and developmental defects, which reflect genomic instability. Based on loss of function of the APT gene, we estimated this mutator phenotype to be at least 130 times higher in the mutants than in wild type. We also found that MSH2 is involved in some but not all the moss responses to genotoxic stresses we tested. Indeed, the Ppmsh2 mutants were more tolerant to cisplatin and show higher sensitivity to UV-B radiations. PpMSH2 gene involvement in HR was studied by assessing gene targeting (GT) efficiency with homologous and homeologous sequences. GT efficiency with homologous sequences was slightly decreased in the Ppmsh2 mutant compared with wild type. Strikingly GT efficiency with homeologous sequences decreased proportionally to sequence divergence in the wild type whereas it remained unaffected in the mutants. Those results demonstrate the role of PpMSH2 in the maintenance of genome integrity and in homologous and homeologous recombination.

BackgroundRecently, much progress has been made to develop more physiologic in vitro models of the respiratory system and improve in vitro simulation of particle exposure through inhalation. Nevertheless, the field of nanotoxicology still suffers from a lack of relevant in vitro models and exposure methods to predict accurately the effects observed in vivo, especially after respiratory exposure. In this context, the aim of our study was to evaluate if exposing pulmonary cells at the air-liquid interface to aerosols of inhalable and poorly soluble nanomaterials generates different toxicity patterns and/or biological activation levels compared to classic submerged exposures to suspensions. Three nano-TiO2 and one nano-CeO2 were used. An exposure system was set up using VitroCell® devices to expose pulmonary cells at the air-liquid interface to aerosols. A549 alveolar cells in monocultures or in co-cultures with THP-1 macrophages were exposed to aerosols in inserts or to suspensions in inserts and in plates. Submerged exposures in inserts were performed, using similar culture conditions and exposure kinetics to the air-liquid interface, to provide accurate comparisons between the methods. Exposure in plates using classical culture and exposure conditions was performed to provide comparable results with classical submerged exposure studies. The biological activity of the cells (inflammation, cell viability, oxidative stress) was assessed at 24 h and comparisons of the nanomaterial toxicities between exposure methods were performed.ResultsDeposited doses of nanomaterials achieved using our aerosol exposure system were sufficient to observe adverse effects. Co-cultures were more sensitive than monocultures and biological responses were usually observed at lower doses at the air-liquid interface than in submerged conditions. Nevertheless, the general ranking of the nanomaterials according to their toxicity was similar across the different exposure methods used.ConclusionsWe showed that exposure of cells at the air-liquid interface represents a valid and sensitive method to assess the toxicity of several poorly soluble nanomaterials. We underlined the importance of the cellular model used and offer the possibility to deal with low deposition doses by using more sensitive and physiologic cellular models. This brings perspectives towards the use of relevant in vitro methods of exposure to assess nanomaterial toxicity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-016-0171-3) contains supplementary material, which is available to authorized users.

Purpose: To develop a molecular tool to detect circulating tumor-derived DNA (ctDNA) in the plasma from patients with uveal melanoma as a marker of tumor burden and monitor treatment efficacy.Experimental Design: A real-time PCR was developed on the basis of bidirectional pyrophosphorolysisactivated polymerization (bi-PAP) for the quantification of ctDNA using 3 0 blocked primer pairs specific for the 3 recurrent mutually exclusive mutations of Ga subunits GNAQ and GNA11.Results: Sensitivity and specificity of bi-PAP were assessed on serial dilutions of tumor DNA in normal DNA for the 3 recurrent mutations. Each assay could detect a single mutated molecule per reaction, whereas 10 4 copies of normal DNA were not detected. The ctDNA was readily detected in plasma of mice bearing uveal melanoma xenografts in amounts proportional to circulating human DNA. Finally, plasma was almost always found positive (20 of 21 tested patients) in a prospective analysis of patients with metastatic uveal melanoma. Conclusions: Bi-PAP assays detect and quantify ctDNA in patients with metastatic uveal melanoma. A prospective study is ongoing to assess the clinical usefulness of ctDNA level in uveal melanoma.