Silver Nanoparticle-Induced Lymphocyte Activation in Zebrafish

Silver nanoparticles (Ag-NPs) are among the most widely used nanomaterials in the world. Nanotoxicological data on these additives remain unclear. The aim of this study is to evaluate the in vivo effects of Ag-NPs bioaccumulation on the hematological cells of adult zebrafish Danio rerio after three weeks of oral exposure. Four concentrations of Ag-NPs (65 nm nanosphere), are used: control group 1 (0.00 g/kg of food), group 2 (0.05 g/kg of food), group 3 (5 g/kg of food) and group 4 (50 g/kg of food). The experiment is conducted in triplicate. Cytological and histological results show, a significant increase in neutrophils associated with a significant decrease in lymphocytes in both group 3 and 4 compared to the control group (p 0,05 and p 0,005, respectively). This reflects an elevated neutrophil/lymphocyte ratio (NLR), suggesting a biased immune response associated with hyperplasia of the hematopoietic tissue and histopathological images of nephrological lesions, following medium to high dose of Ag-NPs intake. Besides, microscopic observation of cell morphology revealed lymphocyte activation only in groups 2 and 3 (p 0,005 and p 0,05, respectively). These results suggest that Ag-NPs induce a dose-dependent bioeffects on the immune system in zebrafish. This study reports that at low doses, Ag-NPs may activate lymphocytes but do not alter the NLR, thus demonstrating an immunostimulatory effect. The present investigation is the first study, as far as we know, reporting that Ag-NPs induce a dose-dependent immunomodulation in zebrafish.