TNF and rheumatoid arthritis: In order to investigate the mechanisms by which triptolide suppressed the angiogenesis in RA, we detected the expression levels of angiogenic activators including TNF-α, IL-1β, VEGF in sera of rats, and TNF-α, IL-17, VEGF, VEGF receptor (VEGFR), Ang-1, Ang-2 and Tie2 in IL-1β-induced HFLS–RA/HUVEC by ELISA assay.