Figure 5.

Internalization of volcanic ash by macrophages induces lysosomal damage and reactive oxygen species (ROS). (A) Light microscopy (20× magnification) and (B) laser scanning microscopy images (63× magnification) of untreated wild-type murine macrophages and macrophages treated with volcanic ash sample MRA5/6/99 for 4 h and stained with Ctx B (red) and DQ-Ovalbumin (DQ-OVA) (green). (C–E) LPS-primed immortalized macrophages were stimulated with 1 mg/ml MRA5/6/99 in the presence or absence of the endocytosis inhibitor latrunculin A (Lat A) (C), the cathepsin B inhibitor CA-074-Me (D), or the ROS scavenger (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylic acid (APDC) (E). Secretion of IL-1β in supernatants was measured by ELISA. Leu-Leu-OMe and nigericin served as lysosomotropic positive control and NLRP3-dependent inflammasome activator, respectively. Representative data from two independent experiments are shown. *p ≤ 0.05, compared to inhibitors (Lat A, Cath B, APDC).