LPS induces the phosphorylation of p38SAPK, ERK, and Akt kinase.

Peripheral blood monocytes cultured with GM-CSF and IL-4 for 7 days (immature MoDCs) were exposed to LPS (100 ng/mL) and, after variable lengths of time, samples were removed and analyzed by probing Western blots and with phosphorylation-specific antibodies. In some cases, the day-7 MoDCs were preincubated with signal transduction pathway inhibitors for 30 minutes before exposure to LPS. (A) The phosphorylation (and hence activation) of p38SAPK induced by LPS occurs within 15 minutes and persists for at least 60 minutes. The lower part shows the same blot probed for total p38SAPK to demonstrate equal loading of samples. (B) The phosphorylation (and hence activation) of Akt and ERK induced by LPS occurs within 30 minutes after exposure of MoDCs to LPS. The phosphorylation of Akt is inhibited if MoDCs are preincubated with the PI3 kinase inhibitor LY294002. Similarly, the phosphorylation of ERK is inhibited if MoDCs are preincubated with the MKK1/MEK inhibitor PD98059. PD98059 and LY294002 were both dissolved in DMSO; therefore, MoDCs that had been incubated with DMSO alone were used as controls (d). The lower part shows the same blot probed for total Akt to demonstrate equal loading of samples. Similar results were obtained in 4 separate experiments.