Alveolar macrophages (AM) exposed to long TiO
nanobelts (NB-2) uniquely form the NALP3 inflammasome. A and B panels show proxy measures for the NALP3 inflammasome formation, IL-1β and IL-18 are significantly enhanced by NB-2 exposure in the presence of a low concentration of the co-stimulant lipopolysaccaride (LPS). These increases were unique to NB-2 exposure in vitro, and they were significantly inhibited by 10 μM of the cathepsin B inhibitor CA-074 Me (respective insets). B, IL-18 was significantly increased in NB-2 exposed cells even with the absence of LPS co-stimulation. In panels C and D, these observations are supported by the in vivo observation of significantly increased IL-1β and IL-18 in the lavage fluid of mice 24 hours following NB-2 instillation (30 μg/mouse). Data expressed as mean ± SEM. Asterisk (*) indicates P < 0.05, double asterisks (**) indicates P < 0.01, and triple asterisks (***) indicates P < 0.001 compared to baseline or control production levels.