Research article

Triptolide, an active compound identified in a traditional Chinese herb, induces apoptosis of rheumatoid synovial fibroblasts

Natsuko Kusunoki¹ , Ryuta Yamazaki^1,2 , Hidero Kitasato³ , Moroe Beppu⁴ , Haruhito Aoki⁴ and Shinichi Kawai¹

¹  Institute of Medical Science, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki-shi, Kanagawa 216-8512, Japan

²  Yakult Central Institute for Microbiological Research, Tokyo, Japan

³  Kitasato University School of Medicine, Kanagawa, Japan

⁴  Department of Orthopaedic Surgery, St. Marianna University School of Medicine, Kanagawa, Japan

author email corresponding author email

BMC Pharmacology 2004, 4:2doi:10.1186/1471-2210-4-2

Published:	17 February 2004

Abstract

Background

Extracts of Tripterygium wilfordii Hook F (TWHF), a traditional Chinese herb, have been reported to show efficacy in patients with rheumatoid arthritis (RA). Since RA is not only characterized by inflammation but also by synovial proliferation in the joints, we examined whether triptolide (a constituent of TWHF) could influence the proliferation of rheumatoid synovial fibroblasts (RSF) by induction of apoptosis.

Results

RSF were obtained from RA patients during surgery and were treated with triptolide under various conditions. The viability and proliferation of RSF were measured by the 4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate (WST-1) assay and by 5-bromo-2'-deoxyuridine incorporation, respectively. Apoptosis was identified by detection of DNA fragmentation using an enzyme-linked immunosorbent assay and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL). The role of caspases in apoptosis of RSF was analyzed by measuring caspase-3 activity. Activation of the peroxisome proliferator-activated receptor (PPAR) γ was assessed by a luciferase reporter gene assay using RSF transfected with a plasmid containing the peroxisome proliferator response element. Triptolide decreased viability, inhibited proliferation, and induced apoptosis of RSF in a concentration-dependent manner at very low (nM) concentrations. Caspase-3 activity was increased by treatment with triptolide and was suppressed by caspase inhibitors. Although PPARγ activation was induced by 15-deoxy-Δ^12,14-prostaglandin J₂, triptolide did not induce it under the same experimental conditions. An extract of TWHF also induced DNA fragmentation in RSF.

Conclusion

The mechanism of action remains to be studied; however, triptolide may possibly have a disease-modifying effect in patients with RA.