Inhibitory effects of triptolide on titanium particle-induced osteolysis and receptor activator of nuclear factor-κB ligand-mediated osteoclast differentiation.

Abstract

We examined the effects of triptolide on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation and on titanium (Ti) particle-induced osteolysis. To examine the effect of triptolide on osteoclast differentiation, bone marrow macrophages (BMMs) were treated with 100ng/mL of RANKL and 30ng/mL of macrophage-colony stimulating factor, or co-cultured with osteoblasts stimulated with 10nM vitamin D3 and 1μM prostaglandin E2 in the presence or absence of triptolide (2.8-14nM). Osteoclast differentiation and activation were assessed using tartrate-resistant acid phosphatase staining, reverse transcriptase-polymerase chain reaction analysis to determine differentiation marker gene expression and pit formation assays. To examine the effect of triptolide on wear debris-induced osteolysis, titanium (Ti) particles were injected into the calvaria of ICR mice. Then, the mice were divided into three groups and were orally administered vehicle, or 16 or 32μg/kg/day triptolide for tendays, followed by histomorphometric analysis. Triptolide suppressed RANKL-mediated osteoclast differentiation of BMMs in a dose-dependent manner. In a co-culture system, osteoblasts treated with triptolide could not induce osteoclast differentiation of BMMs, which was accompanied by down-regulation of RANKL and up-regulation of osteoprotegrin. Moreover, triptolide significantly inhibited bone resorption, and expression of the bone resorption marker genes. RANKL-induced activation of p38, ERK, and JNK was substantially inhibited by triptolide. Further, in a Ti-induced mouse calvarial erosion model, mice perorally administrated with triptolide showed significant attenuation of Ti-mediated osteolysis. Our data indicated that triptolide had an anti-osteoclastic effect and significantly suppressed wear debris-induced osteolysis in mice.