Induction of VEGF Gene Transcription by IL-1 β is Mediated Through Stress-activated MAP Kinases and Sp1 Sites in Cardiac Myocytes

Interleukin-1 β (IL-1 β) is a multipotent cytokine participating in a variety of cardiovascular diseases. In this study, we examined the effects of IL-1 β on the expression of vascular endothelial cell growth factor (VEGF) and pursued the molecular mechanisms underlying this effect. Treatment of cultured neonatal rat cardiac myocytes with IL-1 β increased the levels of VEGF mRNA in a time- and a concentration-dependent manner. These effects were completely abolished by SB203580 and SB202190 (p38 MAPK inhibitors) but not by PD98059 (MEK1 inhibitor), calphostin C (protein kinase C inhibitor), or genistein (tyrosine kinase inhibitor). While IL-1 β phosphorylated c-Jun N-terminus protein kinase (JNK) rapidly and transiently, the effect of IL-1 β on p38 mitogen-activated protein kinase (MAPK) was gradual and persistent. Transient transfection assays showed that IL-1 β increases the transcription from the VEGF promoter. A series of 5-deletion and site-specific mutation analyses indicated that IL-1 β as well as overexpression of p38 MAPK and JNK activate VEGF promoter activity through two G+C-rich sequences located at -73 and -62. Electrophoretic mobility shift and supershift assays showed Sp1 and Sp3 proteins specifically bind to the G+C-rich sequences. The half-life of VEGF mRNA was significantly increased in cells treated with IL-1 β. Together, these results indicate that IL-1β induces VEGF gene expression at both transcriptional and post-transcriptional levels, and IL-1 β evokes p38 MAPK and JNK signalings, which in turn stimulate the transcription of the VEGF gene through Sp1-binding sites. These findings suggest the role of IL-1 β as a cytokine inducing VEGF in cardiac myocytes, and imply that activation of stress-activated MAP kinases regulate Sp1 sites-dependent transcription.