Figure 1. In vivo and in vitro exposure to particulate matter (PM) induces DNA breaks in macrophages. Male C57BL/6 mice, aged 6-8 weeks (n=3) were instilled intratracheally with PM at 100 mg·d-1 for 2 days. After 24 hours lung tissues were collected, and DNA damage was analysed. (A) Lung tissues were stained with TUNEL (green) revealing the level of double-strand DNA breakage generated during apoptosis. The average percentage of TUNEL-positive cells to the total lung tissue cells with DAPI staining were quantified. (B) Representative immunofluorescence images of TUNEL (green) cells in alveolar macrophages are revealed using CD68 (red) staining. (C) Representative images of of alkaline comet assay in seven-day bone marrow–derived macrophages from wildtype mice stimulated with PM at 100 mg·mL-1 for time course (0h, 3h, 6h, 12h, 24h). Percentage of DNA intensity in the comet tail, was quantified. Each dot represents a single cell nucleus, and different colour represents corresponding exposure time(blue for 0h, green for 3h, yellow for 6h, orange for 12h, red for 24h) . The data are presented as means ± SEMs. *p < 0.05; **p < 0.01; ***p < 0.001.