Environmentally relevant fluoride alters nuclear integrity in erythrocytes and induces DNA damage in hepatocytes of zebrafish

The toxicity associated with environmentally relevant concentration of fluoride (F) was investigated in zebrafish ( Danio rerio ). Following exposure to 15 ppm sodium fluoride (NaF; 6.8 ppm F − ), a concentration reported to be present in potable water in different parts of the world, the erythrocytes developed micronuclei and other nuclear anomalies including blebbed, lobed and notched nuclei. F exposure also elicited marked cytoxicity in the hepatocytes in trypan blue dye exclusion test and acridine orange/ ethidium bromide (AO/EtBr) staining. There was upregulation of reactive oxygen species (ROS) generation in the hepatocytes of F-treated fishes, and DNA fragmentation assay revealed compromised nuclear integrity as evident from the smear formation following F exposure. DNA strand scission assay using calf thymus DNA, however, did not show any DNA damage post-F exposure, suggesting that the genotoxic effect was perhaps mediated through ROS generation. Up-regulation of p53, Bax, caspase 9 and caspase 3 gene expressions with concomitant downregulation of anti-apoptotic Bcl-2 gene in treated fishes confirmed the induction of intrinsic apoptotic pathway due to F exposure. The study confirms the toxicity of environmentally relevant concentration of F to aquatic creatures.