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-a (TNF-alpha) 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.