The Immune Toxicity of Titanium Dioxide on Primary Pulmonary Alveolar Macrophages Relies on their Surface Area and Crystal Structure

Surface properties are critical to assess effects of titanium dioxide (TiO₂) primary nanoparticles on the immune function of pulmonary alveolar macrophage (PAMs). In this study the immune toxicity of TiO₂ primary nanoparticles on PAMs relies on their surface area and crystal structure were determined. The primary PAMs of rats exposed to different sizes and crystal structure of TiO₂ particles at different dosages for 24 hrs were evaluated for cytokines, phagocytosis, chemotaxis and surface molecules expression. Nitric oxide (NO) and tumor necrosis factor-α (TNF-α) level of PAMs significantly increased when exposed to TiO₂ primary particles and there were significant association with the exposure total surface area and crystal structure of TiO₂ particles in the former. TiO₂ particles showed significant inhibiting effects on phagocytotic ability, chemotactic ability, Fc receptors and MHC-II molecular expression of macrophages compared with control. Exposure dosage and crystal structure of TiO₂ particles play effects on phagocytotic ability and chemotactic ability of PAMs. These results suggested that TiO₂ nanoparticles could induce the release of inflammatory mediators, initiate the inflammation development and inhibit the immune function of PAMs associated with non-specific immunity and specific immunity relies on surface area and crystal structure. NO activity might be a candidate marker indicating the TiO₂ exposure burden and cell damage in PAMs.