Involvement of c-Jun N-terminal kinase and extracellular signal-regulated kinase 1/2 in EGF-induced angiogenesis.

Angiogenesis is a process during which endothelial cells divide and migrate to form new capillaries from the preexisting blood vessels. The present study was designed to investigate whether MAPKs (mitogen-activated protein kinases) play crucial roles in regulating EGF (epidermal growth factor)-induced endothelial cell angiogenesis. Our results showed that EGF stimulated HUVEC (human umbilical vein endothelial cells) proliferation in a concentration-dependent manner, of which the maximum effective concentration of EGF was 10 ng/ml. Western blot analysis showed that EGF at 10 ng/ml significantly induced the phosphorylation of ERK1/2 (extracellular signal-regulated kinase 1 and 2) and p38 kinase at 5 min, while it induced the phosphorylation of JNK/SAPK (c-Jun N-terminal kinase/stress-activated protein kinase) at 15 min. Further results showed that a JNK/SAPK inhibitor, SP600125, and a specific siRNA JNK/SAPK could both significantly inhibit EGF-induced tube formation in HUVEC cells, and an ERK1/2 inhibitor PD098059 could also block the tube formation in some content, while a p38 inhibitor SB203580 failed to do so. Furthermore, only SP600125 significantly inhibited EGF-induced HUVEC cell proliferation under no cytotoxic concentration, so did JNK/SAPK siRNA. In conclusion, JNK/SAPK and ERK1/2 signals therefore play critical roles in EGF-mediated HUVEC cell angiogenesis.