TNF-α modulates angiopoietin-1 expression in rheumatoid synovial fibroblasts via the NF-κB signalling pathway

Angiopoietin-1 (Ang-1) is one of a family of ligands for the Tie-2 receptor which has been demonstrated to be involved in angiogenesis. Little is known about the regulation of Ang-1 gene expression. We have previously demonstrated that TNF-α is able to up-regulate the expression of Ang-1 mRNA in synovial fibroblasts. This present study investigated the signal transduction pathways involved in the TNF-α induced expression of Ang-1. TNF-α signals primarily through the p38, JNK, MAP kinase, and IKK pathways resulting in the activation of the transcription factors AP-1 and NF-κB. Experiments with inhibitors and siRNA for these various signal transduction pathways revealed that TNF-α stimulation of Ang-1 expression occurs via the NF-κB signal transduction pathway.