Figure 6.

Repeated exposures concentrates Magnéli phases in pulmonary macrophages. (A) Using ICP-MS, we quantified the amount of titanium in the lungs following multiple airway exposures to 100 ppm Ti₆O₁₁ over a 30 day period. (B) Histopathology using H&E stained tissue sections reveled significant airway inflammation LPS treated animals, but no evidence of inflammation in the mice treated with Magnéli phases. Larges areas of macrophages containing Magnéli phases were found in all treated animals (Scale bar = 20 μm). (C) Darkfield images were taken of mouse lungs post-repeated exposures, on day 30. Particles in the tissues were identified by bright punctate dots. Almost all particles were concentrated in macrophages (green arrows). However, small numbers of Ti₆O₁₁ nanoparticles were found associated with alveolar epithelial cells (green arrows). Representative H&E stained lung sections (Scale bar = 50 μm). (D) Phagocytic Index (number of BALF macrophages containing Magnéli phases per 100 cells). (E–G) APAF1 immunohistochemistry staining from (E) saline, (F) LPS, and (G) Magnéli Phase exposed lungs. (G) Following Magnéli Phase exposure, only endothelial cells and macrophages containing particles were broadly positive for APAF1. (E) In saline exposed mice, only endothelial cells were positive for APAF1; (F) whereas, LPS exposure resulted in a range of cell types staining positive for APAF1. Macrophages in each image are identified by red arrows. All data are expressed as mean ± SEM (n = 7/group). **p < 0.01.