Figure 4. The MEK and ERK pathways mediated S1P-promoted PDGF-A expression and angiogenesis. (A) Cells were pretreated for 30 min with PD98059 (10 μM) and U0126 (5 μM), or transfected with MEK and ERK siRNAs, then stimulated with S1P (10 μM). PDGF-A expression was examined by qPCR assays (n=5). (B, C) The CM was applied to EPCs and analyses assessed migratory and tube formation activity (n=4). (D) JJ012 cells were incubated with S1P; MEK and ERK phosphorylation was examined by Western blot assay (n=3). (E, F) JJ012 cells were pretreated with manumycin A, GW5074 and PD98059 for 30 min, then stimulated with S1P (10 μM). MEK and ERK phosphorylation was examined (n=3). Results are expressed as the mean ± SEM. *p < 0.05 as compared with the control group; #p < 0.05 as compared with the S1P-treated group.