Effects and Interaction of Icariin, Curculigoside, and Berberine in Er-Xian Decoction, a Traditional Chinese Medicinal Formula, on Osteoclastic Bone Resorption

Er-Xian decoction (EXD), a traditional Chinese medicine, has been reported to have a protective effect against bone loss in ovariectomized osteoporotic rats, and the inclusion of icariin (I), curculigoside (C), and berberine (B) in EXD displays inhibitory effects on osteoclastic bone resorption. In the present paper, we investigated the interaction and effects of I, C, B, and their combination on bone resorption activity in vitro on osteoclasts derived from rat bone marrow cells. ICB synergistically decreased the formation of bone resorption pits, the number of multinucleated osteoclasts, and the activity of tartrate-resistant acid phosphatase (TRAP) and showed antagonistic or additive effects on cathepsin K activity in the coculture system of osteoblasts and bone marrow cells in the presence of 1, 25-dihydroxyvitamin D(3) and dexamethasone. The combination of ICB also enhanced the inhibitory effects on the formation of F-actin ring, a cytoskeleton structure of osteoclasts induced from bone marrow cells with macrophage colony stimulation factor (M-CSF) and receptor activator of NF-κB ligand (RANKL). In addition, ICB synergistically improved the ratio of protein expression of osteoprotegerin (OPG) and RANKL in osteoblasts and interfered with the mitogen-activated protein kinases (MAPKs) pathway in osteoclast. These results clearly show that I, C, B, and their combination in EXD exert effects of mutual reinforcement. However, IBC does not show an intensified adverse effect in the ovariectomized murine model, as revealed by change in body and uterine weight, confirming the safety of EXD. These observations are in agreement with the rationality of the formula used in this paper.