Inductive Effect of Palmatine on Apoptosis in RAW 264.7 Cells

Osteoporosis is a serious public health problem characterized by low bone density and deterioration of the bone microarchitecture. Current treatment options target either osteoclast resorption or osteoblast formation. It has been reported that berberine, a close structural analog of palmatine, inhibited bone loss in an osteoporosis model. In this study, osseous metabolism was observed in vitro with osteoclast bone resorbing cells. We proved that mouse preosteoclastic cell line (RAW 264.7) has a higher sensitivity to palmatine than mouse osteoblastic cell line (MC3T3-E1); the cell survival rates significantly decreased at 40 μM palmatine. The NO2 (-) level, a metabolic product of nitric monoxide (NO), and iNOS mRNA expression, an osteoclast with NO induced enzyme, also increased with higher dosage of palmatine. Furthermore, it was recognized that the cell viability decrease from palmatine was caused by apoptosis rather than necrosis. Additionally, osteoclast apoptosis from palmatine did not occur when iNOS was inhibited with N(G)-nitro-L-arginine methyl ester hydrochloride (pan NOS inhibitor). These results indicate that palmatine plays an important role in osteoclast apoptosis via the NOS system. Hence, palmatine could be considered as a viable pharmaceutical candidate for osteoporosis bone resorption inhibitor.