* Department of Oral Microbiology and Immunology, College of Dentistry, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea.
† Center for Metabolic Function Regulation (CMFR), School of Medicine, Wonkwang University, Iksan, Jeonbuk 54538, Republic of Korea.
Am J Chin Med. 2017;45(8):1725-1744. doi: 10.1142/S0192415X17500938. Epub 2017 Nov 9.
Puerariae radix, the dried root of Pueraria lobate Ohwi, is known to prevent bone loss in ovariectomized mice; however, the precise molecular mechanisms are not understood. In this study, we investigated the effects and underlying mechanisms of action of Puerariae radix extract (PRE) on receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis. PRE dose-dependently inhibited osteoclast differentiation and formation, decreased the bone-resorbing activity of osteoclasts, and downregulated the expression of osteoclast differentiation marker genes. The expression of osteoclastogenic factors produced by PRE-treated osteoblasts such as RANKL, macrophage colony-stimulating factor (M-CSF), and osteoprotegerin (OPG) was comparable to that of untreated (control) cells. However, the formation of osteoclasts via bone marrow cell and calvaria-derived osteoblast co-cultures was suppressed by PRE treatment. Therefore, the inhibitory effects of PRE on osteoclastogenesis clearly targeted osteoclasts, but not osteoblasts. PRE treatment considerably reduced RANKL-induced mitogen-activated protein kinases (MAPKs) activity, especially c-Jun N-terminal kinase, in osteoclast precursor cells. In addition, PRE markedly suppressed cAMP response element-binding protein (CREB) activation and the induction of peroxisome proliferator-activated receptor gamma coactivator 1β (PGC1β), which stimulate osteoclastogenesis - an effect that was not observed for puerarin and 17-β estradiol. Finally, PRE treatment significantly repressed the expression of c-Fos and the nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), which is a master transcription factor for osteoclastogenesis in vitro and in vivo. Overall, these results strongly suggest that PRE is an effective inhibitor of RANKL-induced osteoclastogenesis and may be a potent therapeutic agent for bone-related diseases such as osteoporosis, rheumatoid arthritis, and periodontitis.
葛根是野葛的干燥根，已知可预防去卵巢小鼠的骨丢失；然而，其确切的分子机制尚不清楚。在这项研究中，我们研究了葛根提取物 (PRE) 对核因子-κB 受体激活配体 (RANKL) 诱导的破骨细胞形成的作用及其潜在的作用机制。PRE 呈剂量依赖性地抑制破骨细胞分化和形成，降低破骨细胞的骨吸收活性，并下调破骨细胞分化标记基因的表达。经 PRE 处理的成骨细胞产生的破骨细胞生成因子，如 RANKL、巨噬细胞集落刺激因子 (M-CSF) 和骨保护素 (OPG) 的表达与未处理（对照）细胞相当。然而，通过骨髓细胞和颅骨衍生的成骨细胞共培养形成的破骨细胞的形成被 PRE 处理所抑制。因此，PRE 对破骨细胞形成的抑制作用显然针对破骨细胞，而不是成骨细胞。PRE 处理显著降低了破骨细胞前体细胞中 RANKL 诱导的丝裂原活化蛋白激酶 (MAPKs) 活性，特别是 c-Jun N 端激酶。此外，PRE 显著抑制 cAMP 反应元件结合蛋白 (CREB) 的激活和过氧化物酶体增殖物激活受体 γ 共激活因子 1β (PGC1β) 的诱导，这刺激破骨细胞形成 - 而对于葛根素和 17-β 雌二醇则没有观察到这种作用。最后，PRE 处理显著抑制了 c-Fos 和激活 T 细胞的核因子细胞质 1 (NFATc1) 的表达，这是体外和体内破骨细胞形成的主要转录因子。总体而言，这些结果强烈表明 PRE 是 RANKL 诱导的破骨细胞形成的有效抑制剂，可能是骨质疏松症、类风湿关节炎和牙周炎等与骨骼相关疾病的有效治疗药物。
