Toxicity and bio-accumulation of inhaled cerium oxide nanoparticles in CD1 mice

Male CD1 mice were subjected to nose-inhalation exposure of CeO2 nanoparticles (NPs) for 0, 7, 14 or 28 days with 14 or 28 days of recovery time at an aerosol concentration of 2 mg/m(3). Markers of lung injury and pro-inflammatory cytokines (interleukin-1beta, tumour necrosis factor-alpha, interleukin-6 and macrophage inflammatory protein-2) in bronchoalveolar lavage fluid (BALF), oxidative stress in lungs, bio-accumulation, and histopathology of pulmonary and extrapulmonary tissues were assessed. BALF analysis revealed the induction of pulmonary inflammation, as evident by an increase in the influx of neutrophils with a significant secretion of pro-inflammatory cytokines that lead to generation of oxidative stress and cytotoxicity, as is evident by induction of lipid peroxidation, depletion of glutathione and increased BALF lactate dehydrogenase and protein. The histopathological examination revealed that these inhaled CeO2 NPs were located all over the pulmonary parenchyma, inducing a severe, chronic, active inflammatory response characterised by necrosis, proteinosis, fibrosis and well-formed discrete granulomas in the pulmonary tissue and tubular degeneration leading to coagulative necrosis in kidneys. Inductively coupled plasma optical emission spectrometer results showed a significant bio-accumulation of these particles in the pulmonary and extrapulmonary tissues, even after one month of post-inhalation exposure. Together, these findings suggest that inhalation exposure of CeO2 NPs can induce pulmonary and extrapulmonary toxicity.