Effects of TiO2 Nanoparticles on Human Myelomonocytic Cell Line THP-1
Abstract
The frequency of exposure to nanoparticles has remarkably increased throughout recent years. Titanium dioxide (TiO2) materials are commonly used for consumer and health care products as well as for technical and medicinal applications. Recently, both suppressive and stimulatory effects of TiO2 nanoparticles on human peripheral blood mononuclear cells have been shown, indicating T-cell - macrophage interactions to be an important target for nanoparticle action.
To address the impact of nanoparticles on isolated monocytes, we investigated effects of TiO2 nanoparticles on the human myelomonocytic cell line THP-1 in vitro and monitored the influence of particle treatment on tryptophan breakdown in unstimulated and lipopolysaccharide (LPS)-stimulated cells in this study.
Treatment with TiO2 bulk material as well as 25 nm-sized material (OCTi60 and P25) showed a trend towards increased kynurenine concentrations as well as kynurenine to tryptophan (Kyn/Trp) in unstimulated cells, although observed changes were not of statistical significance. No effect on tryptophan levels could be observed. Strength of effects was similar for bulk and P25 material, while OCTi60 was less reactive, by contrast to the earlier results obtained in PBMC.
Furthermore, a cellular antioxidant assay (CAA) was applied to investigate pro- or anti-oxidative effects of the 25nm-sized particles in PBMC. Both OCTi60 and P25 nanoparticles induced reactive oxygen species (ROS) formation weakly but significantly in a dose dependent number. However, high oxidative stress conditions, as provoked by peroxylradicals, could cover nanoparticles effects in this system. In sum, data points towards a major effect of TiO2 nanomaterial on T-cells rather than on monocytes/macrophages.