Role of the p38 MAPK in Ang-1–induced IL-8 expression. (A,B) Representative Northern blot and means (± SEM; n = 3) of IL-8 mRNA levels measured after 1 hour of Ang-1 (expressed as 100%) and Ang-1 plus PD169316 or SB203580 (both at 10 μM). *P < .05 compared with Ang-1 alone. (C) Representative Northern blot of IL-8 mRNA expression measured after 1 hour of Ang-1 and Ang-1 plus PD169316 (10 μM), WM (50 nM), or a combination of the 2. Vertical lines in panel A indicate that lanes were not directly adjacent to each other in the original blots. (D) Representative Northern blot of IL-8 mRNA expression measured after 1 hour of Ang-1 and Ang-1 plus PD169316 (10 μM), PD98059 (30 μM), or a combination of the 2. Vertical lines indicate that lanes were not directly adjacent to each other in the original blots. (E) Influence of p38 inhibition on Ang-1–induced Erk1/2 phosphorylation. Serum-starved HUVECs were incubated for 1 hour with SB203580 (10 μM) and were then stimulated with Ang-1 (300 ng/mL) for 5, 15, 30, and 60 minutes. Cells were then collected, and the levels of phosphorylation and total Erk1/2 proteins were detected with immunoblotting. Note the increase in both the intensity and duration of Erk1/2 phosphorylation when SB203580 was present in the medium. (F) Total and phosphorylated Erk1/2, Flag, and p38α proteins detected in HUVECs mock-transfected or transfected with Flag-p38α plasmid.