Titanium Dioxide Particle Type and Concentration Influence the Inflammatory Response in Caco-2 Cells

Titanium dioxide (TiO(2)) nanoparticles are widely used in cosmetics, sunscreens, biomedicine, and food products. When used as a food additive, TiO(2) nanoparticles are used in significant amounts as white food-coloring agents. However, the effects of TiO(2) nanoparticles on the gastrointestinal tract remain unclear. The present study was designed to determine the effects of five TiO(2) particles of different crystal structures and sizes in human epithelial colorectal adenocarcinoma (Caco-2) cells and THP-1 monocyte-derived macrophages. Twenty-four-hour exposure to anatase (primary particle size: 50 and 100 nm) and rutile (50 nm) TiO(2) particles reduced cellular viability in a dose-dependent manner in THP-1 macrophages, but in not Caco-2 cells. However, 72-h exposure of Caco-2 cells to anatase (50 nm) TiO(2) particles reduced cellular viability in a dose-dependent manner. The highest dose (50 µg/mL) of anatase (100 nm), rutile (50 nm), and P25 TiO(2) particles also reduced cellular viability in Caco-2 cells. The production of reactive oxygen species tended to increase in both types of cells, irrespective of the type of TiO(2) particle. Exposure of THP-1 macrophages to 50 µg/mL of anatase (50 nm) TiO(2) particles increased interleukin (IL)-1β expression level, and exposure of Caco-2 cells to 50 µg/mL of anatase (50 nm) TiO(2) particles also increased IL-8 expression. The results indicated that anatase TiO(2) nanoparticles induced inflammatory responses compared with other TiO(2) particles. Further studies are required to determine the in vivo relevance of these findings to avoid the hazards of ingested particles.