Tumor necrosis factor alpha (TNF-α) is a macrophage/monocyte-derived polypeptide which modulates the expression of various genes in vascular endothelial cells and induces angiogenesis. However, the underlying mechanism by which TNF-α mediates angiogenesis is not completely understood. In this study, we assessed whether TNF-α-induced angiogenesis is mediated through TNF-α itself or indirectly through other TNF-α-induced angiogenesis-promoting factors. Cellular mRNA levels of interleukin-8 (IL-8), vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and their receptors were increased after the treatment of human microvascular endothelial cells with TNF-α (100 U/ml). TNF-α-dependent tubular morphogenesis in vascular endothelial cells was inhibited by the administration of anti-IL-8, anti-VEGF, and anti-bFGF antibodies, and coadministration of all three antibodies almost completely abrogated tubular formation. Moreover, treatment with Sp1, NF-κB, and c-Jun antisense oligonucleotides inhibited TNF-α-dependent tubular morphogenesis by microvascular endothelial cells. Administration of a NF-κB antisense oligonucleotide almost completely inhibited TNF-α-dependent IL-8 production and partially abrogated TNF-α-dependent VEGF production, and an Sp1 antisense sequence partially inhibited TNF-α-dependent production of VEGF. A c-Jun antisense oligonucleotide significantly inhibited TNF-α-dependent bFGF production but did not affect the production of IL-8 and VEGF. Administration of an anti-IL-8 or anti-VEGF antibody also blocked TNF-α-induced neovascularization in the rabbit cornea in vivo. Thus, angiogenesis by TNF-α appears to be modulated through various angiogenic factors, both in vitro and in vivo, and this pathway is controlled through paracrine and/or autocrine mechanisms.