Fig. 3.

PM induced oxidative stress in vitro and in vivo. a and b The increased expression of heme oxygenase (HO-1) in THP-1 cells induced by PM at different exposure times and concentrations was determined. c and d The effects of PM on HO-1 expression in RAW 264.7 cells at different exposure times and concentrations. HO-1 expression was increased significantly following a 5 h exposure to PM (F1, F2, and F3, 25 μg/ml). PM induced HO-1 expression in a dose dependent manner, and the effect was inhibited by the antioxidant NAC. Cells were treated with PM (10, 25, or 50 μg/ml) for 5 h. RAW 264.7 cells were incubated with 20 mM NAC for 1 h before addition of 25 μg/ml PM for 5 h. e and f Schematic of PM exposure protocol. PM (F1, F2 and F3: 50 μg per dose; F1(s): 15 μg per dose) or PBS was administered by oropharyngeal aspiration to juvenile BALB/c mice on 17, 19 and 21 days after birth. HO-1 expression in lung tissues was measured by western blotting 48 h after the last exposure to PM or PBS. n = 3–5 mice/group