Expression of ASK1 was up-regulated during LPS-induced endothelial cell apoptosis. (A), HUVECs were cultured in 6-well plate, after 80% confluence, cells were treated with 100 ng/mL LPS for different times point as indicated. Quantitative real time PCR revealed that the expression levels of ASK1 were increased after LPS stimuli. (B), Cell lysates obtained from HUVECs were subjected to western blot. ASK1, phosphorylation of ASK1 at Thr845, and GAPDH were determined by indicated antibodies. (C), the quantitative analysis of HUVECs apoptosis was determined by ELISA assay. Significance is indicated as *P <0.05.