The Effect of Selenium Supplementation in the Prevention of DNA Damage in White Blood Cells of Hemodialyzed Patients: A Pilot Study

Patients with chronic kidney disease (CKD) have an increased incidence of cancer. It is well known that long periods of hemodialysis (HD) treatment are linked to DNA damage due to oxidative stress. In this study, we examined the effect of selenium (Se) supplementation to CKD patients on HD on the prevention of oxidative DNA damage in white blood cells. Blood samples were drawn from 42 CKD patients on HD (at the beginning of the study and after 1 and 3 months) and from 30 healthy controls. Twenty-two patients were supplemented with 200 μg Se (as Se-rich yeast) per day and 20 with placebo (baker's yeast) for 3 months. Se concentration in plasma and DNA damage in white blood cells expressed as the tail moment, including single-strand breaks (SSB) and oxidative bases lesion in DNA, using formamidopyrimidine glycosylase (FPG), were measured. Se concentration in patients was significantly lower than in healthy subjects (P < 0.0001) and increased significantly after 3 months of Se supplementation (P < 0.0001). Tail moment (SSB) in patients before the study was three times higher than in healthy subjects (P < 0.01). After 3 months of Se supplementation, it decreased significantly (P < 0.01) and was about 16% lower than in healthy subjects. The oxidative bases lesion in DNA (tail moment, FPG) of HD patients at the beginning of the study was significantly higher (P < 0.01) compared with controls, and 3 months after Se supplementation it was 2.6 times lower than in controls (P < 0.01). No changes in tail moment was observed in the placebo group. In conclusion, our study shows that in CKD patients on HD, DNA damage in white blood cells is higher than in healthy controls, and Se supplementation prevents the damage of DNA

Evaluation of biological effects of nanomaterials. Part I. Cyto- and genotoxicity of nanosilver composites applied in textile technologies

Objectives: The aim of this study was to investigate the cyto- and genotoxicity of nanocomposites (NCs) and generation of reactive oxygen species (ROS) as a result of particle-cell interactions. Materials and Methods: Titanium dioxide (TiO₂-Ag) and ion-exchange resin (Res-Ag), both coated with silver (Ag), were examined. The murine macrophage J774A.1 cells were incubated in vitro with NC at different concentrations for 24 h. Cytotoxicity was analyzed by the methylthiazolyldiphenyltetrazolium bromide reduction test (MTT reduction test). ROS generation was assessed by incubation of cells with dichlorodihydrofl uorescein diacetate (DCF) and fl ow cytometry. DNA damage was detected by comet assay and included single-strand breaks (SSB), alkali-labile sites (ALS) and oxidative DNA damage after formamidopyrimidine glycosylase (FPG) treatment. The tail moment was used as an indicator of DNA damage. Results: TiO₂-Ag was not cytotoxic up to 200 μg/ml, whereas IC₅₀ for Res-Ag was found to be 23 μg/ml. Intracellular ROS levels were elevated after 4 h of exposure to Res-Ag at the concentration of 50 μg/ml. Both types of NC induced fragmentation of DNA strands, but only one of the composites caused damage to purine bases. TiO₂-Ag induced SSB of DNA at concentrations of 10 and 5 μg/ml. For Res-Ag, a concentration-dependent increase in tail moments was observed. Conclusions: Silver-coated nanocomposites (both TiO₂- Ag and Res-Ag) may cause genotoxic effects in murine macrophages J774A.1. Res-Ag increased generation of ROS which suggested that toxicity of Res-Ag in murine macrophages is likely to be mediated through oxidative stress. This paper will support industry and regulators alike in the assessment of hazards and risks and methods for their mitigation at the earliest possible stage in material and product development

Variation of DNA damage levels in peripheral blood mononuclear cells isolated in different laboratories

This study investigated the levels of DNA strand breaks and formamidopyrimidine DNA glycosylase (FPG) sensitive sites, as assessed by the comet assay, in peripheral blood mononuclear cells (PBMC) from healthy women from five different countries in Europe. The laboratory in each country (referred to as 'centre') collected and cryopreserved PBMC samples from three donors, using a standardised cell isolation protocol. The samples were analysed in 13 different laboratories for DNA damage, which is measured by the comet assay. The study aim was to assess variation in DNA damage in PBMC samples that were collected in the same way and processed using the same blood isolation procedure. The inter-laboratory variation was the prominent contributor to the overall variation. The inter-laboratory coefficient of variation decreased for both DNA strand breaks (from 68 to 26%) and FPG sensitive sites (from 57 to 12%) by standardisation of the primary comet assay endpoint with calibration curve samples. The level of DNA strand breaks in the samples from two of the centres (0.56-0.61 lesions/10(6) bp) was significantly higher compared with the other three centres (0.41-0.45 lesions/10(6) bp). In contrast, there was no difference between the levels of FPG sensitive sites in PBMC samples from healthy donors in the different centres (0.41-0.52 lesion/10(6) bp)