Figure 4

Involvement of the inflammasome, phagocytosis and cathepsin B in inducing the release of mature IL-1β by different silica particles. LPS-primed primary murine macrophages were incubated with silica at equal surface dose (20 cm²/ml) and with ATP (5 mM) as positive control. Culture supernatants were collected after 6 h (1 h for ATP) and cell viability by WST-1 (B, D, F) and IL-1β release (pg/ml) by ELISA (C, E, G) were measured. (A) A representative Western blot analysis conducted on culture supernatants or cell extracts to detect pro-IL-1β (17 kDa) or mature IL-1β (36 kDa) is shown. (B, C) WT mice and mice deficient in the adaptor molecule ASC (ASC^−/−) are compared. Determinations were performed in six replicates (B) or quadruplicate (C) in a single experiment and expressed as the mean ± SD. Cells pre-treated for 1 h with cytochalasin D (5 μM) (D, E) or CA-074-Me (10 μM) (F, G) are compared to untreated cells. Determinations were performed in quadruplicate and expressed as the mean ± SD. Data from one representative experiment out of two (D, E) or one single experiment (F, G) are depicted. *p < 0.05, **p < 0.01 and ***p < 0.001 vs control not exposed to silica particles in each group; ^#p < 0.05, ^##p < 0.01 and ^###p < 0.001 WT vs ASC^−/− or non-treated vs treated with inhibitors, for each sample.