LPS-induced activation of p38 MAPK does not depend on Rho proteins, but p38 MAPK inhibition blocks IL-8 expression in endothelial cells.

(A) HUVECs were exposed to 100 ng/mL LPS for the times indicated; p38 activity was assessed by immunecomplex kinase assay, as described in “Materials and methods,” employing 3pK/MAPKAP-K3 as substrate. Equal gel loading was confirmed by p38 immunoblot. (B) Endothelial cells were pretreated with 10 ng/mL TcdB-10463, 100 ng/mL TcdB-1470, or 200 ng/mL TcsL, each for 1 hour prior to addition of 100 ng/mL LPS for another hour. Inhibition of Rho or Ras proteins had no effect on LPS-induced p38 kinase activity. (C) HUVECs were pretreated with the p38 kinase inhibitor SB 202190 for 30 minutes before stimulation with 100 ng/mL LPS. SB 202190 inhibited IL-8 secretion in a dose-dependent manner. Representative gels (1 of 3 separate experiments) are shown in (A) and (B). Data presented in (C) are mean ± SEM of 4 separate experiments.