Triptolide inhibits rat vascular smooth muscle cell proliferation and cell cycle progression via attenuation of ERK1/2 and Rb phosphorylation

Background

Drug-eluting stents have demonstrated a substantial reduction of restenosis and currently are gaining a leading position in the intervention field. Triptolide, a purified extract from Chinese herb medicine Tripterygium wilfordii hook F, exhibits antiproliferative and pro-apoptotic function in vitro and in vivo. In the present study, we investigated effects of triptolide on in-stent restenosis in vivo and in vitro, and study the biological mechanism of this drug.

Methods

Rat aortic smooth muscle cells were cultured and treated with different concentration of triptolide (0, 1, 10, and 50 nM). For cell viability, we used trypan blue exclusion (TBE) survival assay. Flow cytometry was used to study the influence of triptolide on VSMCs cell cycle. Signal proteins were detected by western blotting analysis. Triptolide coated stents had been implanted in the iliac arteries of New Zealand rabbits. After 4 weeks, the stented iliac artery segments were processed for embedding, staining and histomorphometric analysis.

Results

Triptolide of concentration 10 nM, 50 nM significantly inhibited fetal calf serum-induced VSMC proliferation (p < 0.05). The accumulation of triptolide-treated cells at the G1/S-interphase was dose dependent. Triptolide completely blocked the cell cycle progression at 50 nM. Western blotting analysis showed decreased ERK1/2 MAP kinase phosphorylation level, significantly increased p21^cip1 expression and reduced retinoblastoma protein (pRb) phosphorylation after 24 h of triptolide treatment. 4 weeks after the surgery, the arterial wall morphology was shown that triptolide-coated stent has less neointimal vs bare metal stent.

Conclusions

Our study indicates that triptolide exert inhibitory effect on VSMC proliferation, inactivation of MAPK pathway and modulation of cell cycle proteins p21^cip1 and Rb are relating mechanisms. Triptolide drug-eluting stents attenuated neointimal formation after stent implantation in rabbit vessel. We believe that triptolide may potentially be useful in treating cardiovascular restenosis after PCI.