Apoptosis was increased in low dose LPS-induced mild ARDS but was decreased in high dose LPS-induced server ARDS.

<p>(A) The expression of total and cleaved caspase-3 and XIAP as detected by western blotting. (B) The expression of total and cleaved caspase-8 as detected by western blotting. (C) The number of apoptotic cells by TUNEL staining (400×). (D) TUNEL-positive cell counts per area. The mice were instilled with different concentrations of LPS at doses of 10 mg/kg~40 mg/kg, respectively, while the control group was instilled with PBS. The mice were sacrificed 24 h after LPS instillation. The data are presented as mean±s.e.m; (n = 5). *P<0.05, **P<0.01 versus the control group; ##P<0.01 versus the LPS 10 mg/kg group.