Total Flavonoid Fraction of Rhizoma Drynaria Improves Bone Properties in 265 Ovariectomized Mice and Exerts Estrogen-Like Activities in Rat Osteoblast-Like (UMR-106) Cells
WAI-YIN PANG1, XIN-LUN WANG2, KA-CHUN WONG1, PING-CHUNG LEUNG3, XIN-SHENG YAO2,4 AND MAN-SAU WONG1*
1Food Safety and Technology Research Centre, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
2 College of Traditional Chinese Materia Medica, Shenyang Pharmaceutical University, Shenyang, China
3 Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Hong Kong, China
4 Institute of Traditional Chinese Medicine & Natural Products, College of Pharmacy, Jinan University, Guangzhou, China
ABSTRACT
Rhizoma Drynaria (RD) has been widely used for healing bone fractures or related diseases in traditional Chinese medicine. The present study was designed to determine if RD total flavonoids (RDTF) could exert estrogen-like protective actions on bone. Young C57/BL6J mice were ovariectomized (OVX) and treated orally with RDTF (0.087, 0.173 or 0.346 mg/g/day), 17β-estradiol (2μg/g/day) or its vehicle for 6 weeks. Bone mineral densities (BMD) was measured by peripheral quantitative computed tomography (pQCT). Rat osteoblast-like UMR-106 cells were co-incubated with ER antagonist ICI 182, 780 to determine if the effects of RDTF on osteoblastic functions were ER-dependent. The functional transactivation of ER-α and ER-β as well as ER-αphosphorylation by RDTF were also studied. RDTF increased trabecular-rich BMD at distal femur and lumbar spine in OVX mice. 0.173 mg/g/day was most effective in improving bone properties in OVX mice. The stimulatory effects of RDTF on osteoblastic functionscouldbe abolishedbyco-incubationwithICI182,780inUMR-106cells.Transienttransfectionstudy indicatedthat RDTFdose-dependentlystimulatedERE-dependent luciferaseactivityin UMR-106 cellsvia ER-α and ER-β. Moreover, 0.2 μg/mL ofRDTFsignificantly induced ER-α phosphorylationatserine118inUMR-106 cells.