TiO2 nanoparticles generate superoxide and alter gene expression in human lung cells.

TiO2 nanoparticles are widely used in consumer products and industrial applications, yet little is understood regarding how the inhalation of these nanoparticles impacts long-term health. This is especially important for the occupational safety of workers who process these materials. We used RNA sequencing to probe changes in gene expression and fluorescence microscopy to image intracellular reactive oxygen species (ROS) in human lung cells incubated with low, non-cytotoxic, concentrations of TiO2 nanoparticles. Experiments were designed to measure changes in gene expression following an acute exposure to TiO2 nanoparticles and changes inherited by progeny cells. We observe that TiO2 nanoparticles lead to significant (>2000 differentially expressed genes) changes in gene expression following a 24 hour incubation. Following this acute exposure, the response dissipates with only 34 differentially expressed genes in progeny cells. The progeny cells adapt to this initial exposure, observed when re-challenged with a second acute TiO2 nanoparticle exposure. Accompanying these changes in gene expression is the production of intracellular ROS, specifically superoxide, along with changes in oxidative stress-related genes. These experiments suggest that TiO2 nanoparticles adapt to oxidative stress through transcriptional changes over multiple generations of cells.