Fig. 2.

Phagocytosis is not essential for nanoparticle-induced inflammasome activation. (A) Bone marrow-derived macrophages released IL-1β upon stimulation with MSU (300 μg/mL), TiO₂ 20 nm (200 μg/mL), TiO₂ 80 nm (200 μg/mL), SiO₂ 15 nm (200 μg/mL), and SiO₂ 1.5 μm (200 μg/mL). (B) In contrast, human keratinocytes released mature, cleaved IL-1β only upon exposure to nano-SiO₂ (200 μg/mL) and not to μm-sized SiO₂ (200 μg/mL). (C) Actin polymerization blockade by Cytochalasin D (1 μM) impaired MSU-induced inflammasome activation without affecting TiO₂-dependent IL-1β secretion. Results are representative of three independent experiments. (D) TEM images of THP1 cells stimulated with nano-TiO₂. TiO₂ aggregates were free in the cytoplasm and not located in phagosomes.