Figure 4.

PA inhibits the TNF-α-induced JNK activation in a concentration-dependent manner in human umbilical vein endothelial cells, but not ERK1/2 and p38 activation. Cells were pretreated with PA at the indicated concentrations for 60 min. The cells were then stimulated with 2 ng/ml TNF-α for 15 min for ERK1/2, JNK and p38 activation. Cells were harvested, lysed and used for subsequent analysis. No significant differences in the levels of ERK1/2, JNK and p38 were observed using immunoblot analysis with anti-ERK1/2, -JNK and -p38 antibodies. PA, protocatechuic aldehyde; FN, fibronectin; TNF-α, tumor necrosis factor-α; p-ERK1/2, phosphorylated extracellular signal-regulated kinase 1 and 2; JNK, c-Jun N-terminal kinase; p38, p38 mitogen-activated protein kinase.