Fig. 6.

Effect of U0126 on cell growth inhibition by triptolide (TP), vanadate, and mitogen-activated protein kinase phosphatase-1 (MKP-1) small interfering RNA (siRNA). A : Immortalized HT22 cells were transiently transfected with MKP-1 siRNA, or treated for 6 h with 0.5 µM of TP or 10 µM of vanadate in the presence or absence of 10 µM of U0126. Phosphorylation and expression of the extracellular signal-regulated kinase-1/2 were examined by Western blot analysis as described in materials and methods. Representative Western blots of three independent experiments are shown. B : Immortalized HT22 cells were transfected with MKP-1 siRNA or treated for 24 h with 0.5 µM of TP or 10 µM of vanadate in the presence or absence of 10 µM of U0126. Cell proliferation was determined by ³H-thymidine incorporation, as described in materials and methods. Values represent mean ± SE of four replicates in three different experiments. ^*p < 0.05.