A harmonized and standardized in vitro approach produces reliable results on silver nanoparticles toxicity in different cell lines.

Despite the widespread use of silver nanoparticles (AgNPs) in different fields and the amount of investigations available, to date, there are many contradictory results on their potential toxicity. In the present study, extensively characterized 20-nm AgNPs were investigated using optimized protocols and standardized methods to test several toxicological endpoints in different cell lines. The agglomeration/aggregation state of AgNPs in culture media was measured by dynamic light scattering (DLS).

Use of a common European approach for nanomaterials' testing to support regulation: a case study on titanium and silicon dioxide representative nanomaterials.

The European Union (EU) continuously takes ensuring the safe use of manufactured nanomaterials (MNMs) in consumer products into consideration. The application of a common approach for testing MNMs, including the use of optimized protocols and methods' selection, becomes increasingly important to obtain reliable and comparable results supporting the regulatory framework. In the present study, we tested four representative MNMs, two titanium dioxides (NM100 and NM101) and two silicon dioxides (NM200 and NM203), using the EU FP7-NANoREG approach, starting from suspension and dispersion preparations, through to their characterization and final evaluation of biological effects.

Critical issues in genotoxicity assessment of TiO nanoparticles by human peripheral blood mononuclear cells.

In the last years, a number of in vitro studies have been performed to assess the genotoxic activity of titanium dioxide (TiO ). To resolve the contradictory results, in this study, we investigated the genotoxic activity of commercial TiO nanoparticles (NPs) and microparticles of different forms (anatase, rutile and mix of both). We evaluated micronucleus formation in stimulated lymphocytes, as well as DNA strand breaks and 8-oxo-7,8-dihydro-2'-deoxyguanosine in peripheral blood mononuclear cells (PBMCs), a mixed population of lymphocytes and monocytes.

Increased micronucleus frequency in peripheral blood lymphocytes predicts the risk of bladder cancer.

Background: Bladder cancer (BC) is among the most common malignancies worldwide. The identification of new biomarkers for early BC detection, recurrence/progression is urgently needed. The cytokinesis-block micronucleus assay (CBMN) evaluates chromosome damage in cultured human lymphocytes and micronuclei (MN) provide a convenient and reliable index of both chromosome breakage and loss.

An altered redox balance and increased genetic instability characterize primary fibroblasts derived from xeroderma pigmentosum group A patients.

Xeroderma pigmentosum (XP)-A patients are characterized by increased solar skin carcinogenesis and present also neurodegeneration. XPA deficiency is associated with defective nucleotide excision repair (NER) and increased basal levels of oxidatively induced DNA damage. In this study we search for the origin of increased levels of oxidatively generated DNA lesions in XP-A cell genome and then address the question of whether increased oxidative stress might drive genetic instability.

Different mechanisms are involved in oxidative DNA damage and genotoxicity induction by ZnO and TiO2 nanoparticles in human colon carcinoma cells.

In this work we investigated the genotoxicity of zinc oxide and titanium dioxide nanoparticles (ZnO NPs; TiO2 NPs) induced by oxidative stress on human colon carcinoma cells (Caco-2 cells). We measured free radical production in acellular conditions by Electron Paramagnetic Resonance technique and genotoxicity by micronucleus and Comet assays. Oxidative DNA damage was assessed by modified Comet assay and by measuring 8-oxodG steady state levels.

Gene promoter methylation and DNA repair capacity in monozygotic twins with discordant smoking habits.

The influence of DNA repair capacity, plasma nutrients and tobacco smoke exposure on DNA methylation was investigated in blood cells of twenty-one couples of monozygotic twins with discordant smoking habits. All study subjects had previously been characterized for mutagen sensitivity with challenge assays with ionizing radiation in peripheral blood lymphocytes. Plasma levels of folic acid, vitamin B12 and homocysteine were also available from a previous investigation.

DNA damage response in monozygotic twins discordant for smoking habits.

Previous studies in twins indicate that non-shared environment, beyond genetic factors, contributes substantially to individual variation in mutagen sensitivity; however, the role of specific causative factors (e.g. tobacco smoke, diet) was not elucidated.

Comparative study of ZnO and TiO₂ nanoparticles: physicochemical characterisation and toxicological effects on human colon carcinoma cells.

Despite human gastrointestinal exposure to nanoparticles (NPs), data on NPs toxicity in intestinal cells are quite scanty. In this study we evaluated the toxicity induced by zinc oxide (ZnO) and titanium dioxide (TiO₂) NPs on Caco-2 cells. Only ZnO NPs produced significant cytotoxicity, evaluated by two different assays.

The cross talk between pathways in the repair of 8-oxo-7,8-dihydroguanine in mouse and human cells.

Although oxidatively damaged DNA is repaired primarily via the base excision repair (BER) pathway, it is now evident that multiple subpathways are needed. Yet, their relative contributions and coordination are still unclear. Here, mouse embryo fibroblasts (MEFs) from selected nucleotide excision repair (NER) and/or BER mouse mutants with severe (Csb(m/m)/Xpa(-/-) and Csb(m/m)/Xpc(-/-)), mild (Csb(m/m)), or no progeria (Xpa(-/-), Xpc(-/-), Ogg1(-/-), Csb(m/m)/Ogg1(-/-)) or wild-type phenotype were exposed to an oxidizing agent, potassium bromate, and genomic 8-oxo-7,8-dihydroguanine (8-oxoGua) levels were measured by HPLC-ED.

Unsuitability of lymphoblastoid cell lines as surrogate of cryopreserved isolated lymphocytes for the analysis of DNA double-strand break repair activity.

As first task of a comprehensive investigation on DNA repair genotype-phenotype correlations, the suitability of Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs) as surrogate of cryopreserved peripheral blood mononuclear cells (PBMCs) in DNA repair phenotypic assays was evaluated. To this aim the amount of DNA damage induced by gamma-rays and DNA repair capacity were evaluated in unstimulated (G(0)) and mitogen-simulated (G(2)) PBMC from 20 healthy subjects and in EBV-transformed LCL obtained from the same individuals. Phosphorylation of histone H2AX, micronuclei and chromosomal aberrations were the end-points investigated.

A role for oxidized DNA precursors in Huntington's disease-like striatal neurodegeneration.

Several human neurodegenerative disorders are characterized by the accumulation of 8-oxo-7,8-dihydroguanine (8-oxodG) in the DNA of affected neurons. This can occur either through direct oxidation of DNA guanine or via incorporation of the oxidized nucleotide during replication. Hydrolases that degrade oxidized purine nucleoside triphosphates normally minimize this incorporation.

Suitability of cryopreserved isolated lymphocytes for the analysis of micronuclei with the cytokinesis-block method.

In order to assess the applicability of the cytokinesis-block micronucleus assay to frozen cells in human biomonitoring and in vitro radiosensitivity studies, basal and radiation-induced micronuclei and nucleoplasmic bridges (NPBs) were analysed in 28 lymphocyte samples stored frozen from 18 to 123 weeks. All samples successfully proliferated and produced a sufficient number of binucleated cells to be analysed. The length of the cryopreservation period did not influence cell proliferation, nor the incidence of micronuclei and NPBs, both in untreated and irradiated cells.

An increased micronucleus frequency in peripheral blood lymphocytes predicts the risk of cancer in humans.

The frequency of micronuclei (MN) in peripheral blood lymphocytes (PBL) is extensively used as a biomarker of chromosomal damage and genome stability in human populations. Much theoretical evidence has been accumulated supporting the causal role of MN induction in cancer development, although prospective cohort studies are needed to validate MN as a cancer risk biomarker. A total of 6718 subjects from of 10 countries, screened in 20 laboratories for MN frequency between 1980 and 2002 in ad hoc studies or routine cytogenetic surveillance, were selected from the database of the HUman MicroNucleus (HUMN) international collaborative project and followed up for cancer incidence or mortality.

Effects of folic acid deficiency and MTHFR C677T polymorphism on spontaneous and radiation-induced micronuclei in human lymphocytes.

Folic acid plays a key role in the maintenance of genomic stability, providing methyl groups for the conversion of uracil to thymine and for DNA methylation. Besides dietary habits, folic acid metabolism is influenced by genetic polymorphism. The C677T polymorphism of the methylene-tetrahydrofolate reductase (MTHFR) gene is associated with a reduction of catalytic activity and is suggested to modify cancer risk differently depending on folate status.

The effects of GSTM1 and GSTT1 polymorphisms on micronucleus frequencies in human lymphocytes in vivo.

The influence of genetic polymorphisms in GSTM1 and GSTT1 genes on micronucleus frequencies in human peripheral blood lymphocytes was assessed through a pooled analysis of data from seven laboratories that did biomonitoring studies using the in vivo cytokinesis-block micronucleus assay. A total of 301 nonoccupationally exposed individuals (207 males and 94 females) and 343 workers (237 males and 106 females) occupationally exposed to known or suspected genotoxic substances were analyzed by Poisson regression. The results of the pooled analysis indicate that the GSTT1 null subjects had lower micronucleus frequencies than their positive counterparts in the total population (frequency ratio, 0.

Intra- and inter-laboratory variation in the scoring of micronuclei and nucleoplasmic bridges in binucleated human lymphocytes. Results of an international slide-scoring exercise by the HUMN project.

One of the objectives of the HUman MicroNucleus (HUMN) project is to identify the methodological variables that have an important impact on micronucleus (MN) or micronucleated (MNed) cell frequencies measured in human lymphocytes using the cytokinesis-block micronucleus assay. In a previous study we had shown that the scoring criteria used were likely to be an important variable. To determine the extent of residual variation when laboratories scored cells from the same cultures using the same set of standard scoring criteria, an inter-laboratory slide-scoring exercise was performed among 34 laboratories from 21 countries with a total of 51 slide scorers involved.

Biomonitoring of primary aluminium industry workers: detection of micronuclei and repairable DNA lesions by alkaline SCGE.

The genetic effects of occupational exposure to low polycyclic aromatic hydrocarbon (PAH) concentrations were investigated in primary aluminium industry workers. The study subjects were employed in a plant that uses pre-baked anode cells, and has relatively low PAH contamination. Forty-two male workers belonging to different job categories (anode fabrication, baking, rodding, electrolysis, maintenance), together with 16 male local residents with no occupational exposure to PAHs were selected for the analysis of micronuclei and DNA lesions in peripheral lymphocytes.

Influence of donor age on vinblastine-induced chromosome malsegregation in cultured peripheral lymphocytes.

The incidence of spontaneous aneuploidy in human somatic and germ cells is known to be positively associated with aging. However, the influence of age on the individual susceptibility to chemically induced chromosome malsegregation has not been elucidated. In this study the spindle poison vinblastine (VBL) was used as a model compound to assess the influence of donor age on chemically induced chromosome malsegregation in cultured lymphocytes.