Size effects of nanomaterials on lung inflammation and coagulatory disturbance

Effects of nano-sized materials (nanomaterials) on subjects with predisposing inflammatory disorders have not been well elucidated. This study examined the effects of pulmonary exposure to TiO2 nanomaterials on lung inflammation induced by lipopolysaccharide (LPS) and consequent systemic inflammation with coagulatory disturbance in mice, in particular regarding their size-dependency. Also, gene expression pattern in the lung was compared among the experimental groups using cDNA microarray analysis. ICR male mice were divided into 8 experimental groups that intratracheally received vehicle, three sizes (15, 50, 100 nm) of TiO2 nanomaterials (8 mg/kg), LPS (2.5 mg/kg), or LPS plus nanomaterials. Twenty four h after the treatment, these nanomaterials exacerbated the lung inflammation and vascular permeability elicited by LPS, with an overall trend of amplified lung expressions of cytokines such as interleukin (IL)-1beta, macrophage chemoattractant protein (MCP)-1, and keratinocyte chemoattractant (KC). LPS plus nanomaterials, especially of a size less than 50 nm, elevated circulatory levels of fibrinogen, IL-1beta, MCP-1, and KC, and von Willebrand factor as compared with LPS alone. The enhancement tended overall to be greater with the smaller nanomaterials than with the larger ones. cDNA microarray analyses revealed that there was no difference in gene expression pattern between the LPS group and the LPS + nanomaterial. These results suggest that nanomaterials exacerbate lung inflammation related to LPS with systemic inflammation and coagulatory disturbance, and that the exacerbation is more prominent with smaller nanomaterials than with larger ones.