Genotoxicity of inhaled nanosized TiO2 in mice

Nanosafety Research Center, Finnish Institute of Occupational Health, FI-00250 Helsinki, Finland.
Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis (Impact Factor: 3.68). 11/2011; 745(1-2):58-64. DOI: 10.1016/j.mrgentox.2011.10.011
Source: PubMed


In vitro studies have suggested that nanosized titanium dioxide (TiO(2)) is genotoxic. The significance of these findings with respect to in vivo effects is unclear, as few in vivo studies on TiO(2) genotoxicity exist. Recently, nanosized TiO(2) administered in drinking water was reported to increase, e.g., micronuclei (MN) in peripheral blood polychromatic erythrocytes (PCEs) and DNA damage in leukocytes. Induction of micronuclei in mouse PCEs was earlier also described for pigment-grade TiO(2) administered intraperitoneally. The apparent systemic genotoxic effects have been suggested to reflect secondary genotoxicity of TiO(2) due to inflammation. However, a recent study suggested that induction of DNA damage in mouse bronchoalveolar lavage (BAL) cells after intratracheal instillation of nanosized or fine TiO(2) is independent of inflammation. We examined here, if inhalation of freshly generated nanosized TiO(2) (74% anatase, 26% brookite; 5 days, 4 h/day) at 0.8, 7.2, and (the highest concentration allowing stable aerosol production) 28.5 mg/m(3) could induce genotoxic effects in C57BL/6J mice locally in the lungs or systematically in peripheral PCEs. DNA damage was assessed by the comet assay in lung epithelial alveolar type II and Clara cells sampled immediately following the exposure. MN were analyzed by acridine orange staining in blood PCEs collected 48 h after the last exposure. A dose-dependent deposition of Ti in lung tissue was seen. Although the highest exposure level produced a clear increase in neutrophils in BAL fluid, indicating an inflammatory effect, no significant effect on the level of DNA damage in lung epithelial cells or micronuclei in PCEs was observed, suggesting no genotoxic effects by the 5-day inhalation exposure to nanosized TiO(2) anatase. Our inhalation exposure resulted in much lower systemic TiO(2) doses than the previous oral and intraperitoneal treatments, and lung epithelial cells probably received considerably less TiO(2) than BAL cells in the earlier intratracheal study.

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Available from: Antti Joonas Koivisto, Jan 12, 2014
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    • "Significant increase in the MN frequency was observed in PCEs, when 500 mg/kg/bw of titanium oxide (TiO 2 )–NPs were administered in drinking water for 5 days (Trouiller et al. 2009). On the contrary, when C57BL/6J mice were exposed to TiO 2 –NPs by inhalation route for 5 days (4 h/day) at 0.8, 7.2 and 28.5 mg/m 3 and MN were analyzed by acridine orange staining in blood PCEs collected 48 h after the last exposure, insignificant effect on the level of DNA damage in lung epithelial cells or MN in PCEs was observed , suggesting no genotoxic effects by the 5-day inhalation exposure to nanosized TiO 2 (Lindberg et al. 2012). Our results showed a decrease in MI value in Cr 2 O 3 –NPs and MPs compared to control groups. "
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    ABSTRACT: The nanotechnology industry has advanced rapidly in the last 10 years giving rise to the growth of the nanoparticles (NPs) with great potential in various arenas. However, the same properties that make NPs interesting raise concerns because their toxicity has not been explored. The in vivo toxicology of chromium oxide (Cr2O3)-NPs is not known till date. Therefore, this study investigated the 28-day repeated toxicity after 30, 300 and 1000 mg/kg body weight (bw)/day oral treatment with Cr2O3-NPs and Cr2O3 microparticles (MPs) in Wistar rats. The mean size of Cr2O3-NPs and Cr2O3-MPs was 34.89 ± 2.65 nm and 3.76 ± 3.41 μm, respectively. Genotoxicity was assessed using comet, micronucleus and chromosomal aberration (CA) assays. The results revealed a significant increase in DNA damage in peripheral blood leucocytes and liver, micronuclei and CA in bone marrow after exposure of 300 and 1000 mg/kg doses of Cr2O3-NPs and Cr2O3-MPs only at 1000 mg/kg bw/day. Cr biodistribution was observed in all the tissues in a dose-dependent manner. The maximum amount of Cr was found in the kidneys and least in the brain of the treated rats. More of the Cr was excreted in the faeces than in the urine. Furthermore, nanotreated rats displayed much higher absorption and tissue accumulation. These findings provide initial data of the probable genotoxicity and biodistribution of NPs and MPs of Cr2O3 generated through repeated oral treatment.
    Environmental Science and Pollution Research 10/2015; DOI:10.1007/s11356-015-5622-0 · 2.83 Impact Factor
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    • "Alltogether 46 studies investigating the in vivo genotoxicity of nanomaterials were identified by literature search. 19 of these studies were negative (Lindberg et al., 2012; Landsiedel et al., 2010; Saber et al., 2011; Naya et al., 2012; Rehn et al., 2003; Boisen et al., 2012; Ema et al., 2012; Wessels et al., 2011; Wu et al., 2010; Estevanato et al., 2011; Kim et al., 2011; Kim et al., 2008; Schulz et al., 2012; Sayes et al., 2010; Dandekar et al., 2010; Shinohara et al., 2009; Sadiq et al., 2012; Tavares et al., 2012; Li et al., 2012b). Note that most of these studies do not indicate a lack of evidence for genotoxicity as the doses tested were low and/or it was not shown that the material reached the tissue investigated for genotoxicity in sufficient amounts. "
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    ABSTRACT: Nanotechnology offers enormous potential for technological progress. Fortunately, early and intensive efforts have been invested in investigating toxicology and safety aspects of this new technology. However, despite there being more than 6,000 publications on nanotoxicology, some key questions still have to be answered and paradigms need to be challenged. Here, we present a view on the field of nanotoxicology to stimulate the discussion on major knowledge gaps and the critical appraisal of concepts or dogma. First, in the ongoing debate as to whether nanoparticles may harbour a specific toxicity due to their size, we support the view that there is at present no evidence of 'nanospecific' mechanisms of action; no step-change in hazard was observed so far for particles below 100 nm in one dimension. Therefore, it seems unjustified to consider all consumer products containing nanoparticles a priori as hazardous. Second, there is no evidence so far that fundamentally different biokinetics of nanoparticles would trigger toxicity. However, data are sparse whether nanoparticles may accumulate to an extent high enough to cause chronic adverse effects. To facilitate hazard assessment, we propose to group nanomaterials into three categories according to the route of exposure and mode of action, respectively: Category 1 comprises nanomaterials for which toxicity is mediated by the specific chemical properties of its components, such as released ions or functional groups on the surface. Nanomaterials belonging to this category have to be evaluated on a case-by-case basis, depending on their chemical identity. Category 2 focuses on rigid biopersistent respirable fibrous nanomaterials with a specific geometry and high aspect ratio (so-called WHO fibres). For these fibres, hazard assessment can be based on the experiences with asbestos. Category 3 focuses on respirable granular biodurable particles (GBP) which, after inhalation, may cause inflammation and secondary mutagenicity that may finally lead to lung cancer. After intravenous, oral or dermal exposure, nanoscaled GBPs investigated apparently did not show 'nanospecific' effects so far. Hazard assessment of GBPs may be based on the knowledge available for granular particles. In conclusion, we believe the proposed categorization system will facilitate future hazard assessments.
    Archives of Toxicology 10/2014; DOI:10.1007/s00204-014-1383-7 · 5.98 Impact Factor
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    • "As concerns in vivo investigations , a significant increase in DNA strand breaks and MN formation was detected in the peripheral blood cells of TiO 2 - NP treated animals , as compared with controls ( Trouiller et al . 2009 ; Song et al . 2012 ) . However , the genotoxic effects of TiO 2 - NPs were not confirmed in two other studies ( Lindberg et al . 2012 , Sadiq et al . 2012 ) . These conflicting results may be explained , again , by the differences in terms of TiO 2 crystalline structure , route of exposure and administered dose . Other types of metallic or metal oxide NPs , such as CuO - , Fe 2 O 3 - , Fe 3 O 4 , MnO 2 - , Al 2 O 3 - , Ag - and silica NPs , were reported to induce a d"
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