Evaluation of multi-endpoint assay to detect genotoxicity and oxidative stress in mice exposed to sodium fluoride.

Fluoride compounds are naturally present in soil, water and food. The objective of this study was to investigate the genotoxic and oxidative damage induced by chronic fluoride exposure on mammalian cells in vivo. For this purpose, the genotoxic potential was investigated in bone marrow cells by the micronucleus test, chromosome aberration assay and comet assay (DNA strand breaks). In addition, DNA damage was evaluated in soft tissues and organs like spleen, liver and kidney cells. The oxidative damage was assessed by selective biochemical parameters by the measurement of lipid peroxidation, reduced glutathione (GSH), glutathione S-transferase (GST) and catalase (CAT) activity in liver. Adult Swiss albino male mice were exposed to sodium fluoride in drinking water at the concentrations of 4, 12 and 20mg/L for 30 consecutive days. Control groups (vehicle and positive) were also included. Animals were sacrificed; bone marrow and soft tissue samples were collected and subjected to series of assays respectively. We observed that NaF exposure, at the various concentrations tested caused a significant increase in the frequency of micronucleus (MN) in polychromatic erythrocytes (PCEs), structural chromosome aberrations in bone marrow cells. With the exception of the spleen cells, DNA damage was observed in bone marrow cells as well as in kidney and liver cells. We found an increase in lipid peroxidation, and catalase activity as well as decrease in glutathione activity (GSH and GST) in liver of mice respectively which were exposed to sodium fluoride. In conclusion, the data obtained clearly documents that NaF exhibits genotoxic activity and enhanced oxidative damage in mouse model.

In vitro and in vivo genotoxicity of silver nanoparticles.

The biocidal effect of silver nanoparticles (Ag-np) has resulted in their incorporation into consumer products. While the population exposed to Ag-np continues to increase with ever new applications, Ag-np remains a controversial research area with regard to their toxicity in biological systems. Here a genotoxic and cytotoxic approach was employed to elucidate the activity of Ag-np in vitro and in vivo. Characterization of Ag-np using scanning electron microscopy revealed a size range of 90-180nm. Cytotoxic potential of Ag-np was evaluated in human lymphocytes via cell viability assay (Trypan blue dye exclusion method, MTT and WST assay). The uptake and incorporation of Ag-np into the lymphocytes was confirmed by flow cytometry. Additionally apoptosis (AnnexinV-FITC-PI staining) and DNA strand breaks (comet assay) in human lymphocytes revealed that Ag-np at concentration 25µg/ml can cause genotoxicity. In vivo experiments on plants (Allium cepa and Nicotiana tabacum) and animal (Swiss albino male mice) showed impairment of nuclear DNA. Induction of oxidative stress was also studied. The DNA damage and chromosomal aberrations raise the concern about the safety associated with applications of the Ag-np. A single ip administration of Ag-np gave a significant (P≤0.05) increase in the frequency of aberrant cells and Tail DNA percent at concentrations 10mg/kg body weight and above. Results of comet assay in A. cepa and N. tabacum demonstrated that the genotoxic effect of Ag-np was more pronounced in root than shoot/leaf of the plants. The present study indicated a good correlation between the in vitro and in vivo experiments. Therefore the biological applications employing Ag-np should be given special attention besides adapting the antimicrobial potential.