Effects of nanosized titanium dioxide on innate immune system of fathead minnow (Pimephales promelas Rafinesque, 1820)

Effects of nanosized (<100 nm) titanium dioxide (TiO2) particles on fish neutrophils and immune gene expression was investigated using the fathead minnow (Pimpehales promelas). Expanded use of TiO2 in the cosmetic industry has increased the potential exposure risk to aquatic ecosystems and human health. Effects of nano-TiO2 on neutrophil function of the fathead minnow was investigated using oxidative burst, neutrophil extracellular traps (NETs) release and degranulation of primary granules. The innate immune gene expression was determined with quantitative PCR (qPCR). Application of 0.1 μg mL−1 of nano-TiO2in vitro stimulated oxidative burst and NET release. Intraperitoneal injection of 10 μg g−1 of nano-TiO2 caused a significant decrease in oxidative burst, NETs release and degranulation (21%; 11%; and 30%, decrease, respectively). Fish exposed to nano-TiO2 for 48 h in vivo had significantly increased expression of interleukin 11, macrophage stimulating factor 1, and neutrophil cytosolic factor 2 (4; 2.5; and 2 fold increase, respectively). Nano-TiO2 has potential to interfere with the evolutionary conserved innate immune system responses, as evidenced with observed changes in gene expression and neutrophil function. This finding encourages the use of fish models in the studies of nanoparticle immunotoxicity. The lowest significant response concentration studied in vitro is four times greater than the estimated environmental concentration for TiO2 (0.025 μg mL−1) causing concern about potential impact of nano-TiO2 on aquatic animals and ecosystems.