Oxidative and cytotoxic stress induced by inorganic granular and fibrous particles.

The hazards of granular and fibrous particles have been associated with the generation of reactive oxygen species (ROS), which in turn is often associated with physicochemical properties exhibited by these particles. In the present study, the ability of various types of fibrous and granular dusts to generate oxidative stress, and their cytotoxicity, was investigated. Biopersistent granular dusts employed in the present study included micro‑ and nanosized titanium dioxide with rutile or anatase crystal structure modifications. Additionally, glass fibres, chrysotile and crocidolite asbestos representative of fibrous dust were selected. Detailed characterisation of particles was performed using scanning electron microscopy, and the effect of exposure to these particles on cell viability and intracellular ROS generation was assessed by PrestoBlue and 2',7'‑dichlorofluorescein assays, respectively. A549 human lung epithelial adenocarcinoma cells were exposed to increasing concentrations (0.1‑10 µg/cm2) of particles and fibres for 24 h. Subsequently, the gene expression of X‑linked inhibitor of apoptosis (XIAP), superoxide dismutase (SOD)1 and SOD2 were analysed by reverse transcription‑quantitative polymerase chain reaction. All investigated granular particles induce ROS production in A549 lung carcinoma cells within 24 h. Hematite increased ROS production in a dose‑dependent manner. A concentration of >1 µg/cm2 TiO2 na with its disordered surface, demonstrated the greatest ability to generate ROS. Therefore, the crystalline surface structure of the particle may be considered as a determinant of the extent of ROS induction by the particle. Fibrous particle compared with granular particles were associated with a lower ability to generate ROS. Glass fibres did not significantly increase ROS production in A549 cells, but elevated gene expression of SOD2 was observed. The results demonstrated that in general, the ability of particles to generate ROS depends on their number and crystal phase. Therefore, the present study helps to understand the cause of particle toxicity.