Viereck Volker, Emons Günter, Lauck Vanessa, Frosch Karl-Heinz, Blaschke Sabine, Gründker Carsten, Hofbauer Lorenz C
Department of Obstetrics and Gynecology, Georg-August-University of Goettingen, Goettingen, D-37075, Germany.
Biochem Biophys Res Commun. 2002 Mar 1;291(3):680-6. doi: 10.1006/bbrc.2002.6510.
Bisphosphonates are potent antiresorptive drugs commonly employed in the treatment of metabolic bone diseases. Despite their frequent use, the mechanisms of bisphosphonates on bone cells have largely remained unclear. Receptor activator of nuclear factor-kappaB ligand (RANKL) is essential for osteoclast formation and activation, whereas osteoprotegerin (OPG) neutralizes RANKL. Various osteotropic drugs have been demonstrated to modulate osteoblastic production of RANKL and OPG. In this study, we assessed the effects of the bisphosphonates pamidronate (PAM) and zoledronic acid (ZOL) on OPG mRNA steady-state levels (by semiquantitative RT-PCR) and protein production (by ELISA) in primary human osteoblasts (hOB). PAM increased OPG mRNA levels and protein secretion by hOB by up to 2- to 3-fold in a dose-dependent fashion with a maximum effect at 10(-6) M (P < 0.001) after 72 h. Similarly, ZOL enhanced OPG gene expression and protein secretion by hOB in a dose-dependent fashion with a maximum effect at 10(-8) M after 72 h, consistent with the higher biological potency of ZOL. Time course experiments indicated a stimulatory effect of PAM and ZOL on osteoblastic OPG protein secretion by 6-fold, respectively (P < 0.001). Pretreatment with PAM and ZOL prevented the inhibitory effects of the glucocorticoid dexamethasone on OPG mRNA and protein production. Analysis of cellular markers of osteoblastic differentiation revealed that PAM and ZOL induced type I collagen secretion and alkaline phosphatase activity by 2- and 4-fold, respectively (P < 0.0001 by ANOVA). In conclusion, our data suggest that bisphosphonates modulate OPG production by normal human osteoblasts, which may contribute to the inhibition of osteoclastic bone resorption. Since, OPG production increases with osteoblastic cell maturation, enhancement of OPG by bisphosphonates could be related to their stimulatory effects on osteoblastic differentiation.
双膦酸盐是常用于治疗代谢性骨病的强效抗吸收药物。尽管它们被频繁使用，但双膦酸盐对骨细胞的作用机制在很大程度上仍不清楚。核因子-κB受体活化因子配体（RANKL）对破骨细胞的形成和活化至关重要，而骨保护素（OPG）可中和RANKL。各种促骨药物已被证明可调节成骨细胞中RANKL和OPG的产生。在本研究中，我们评估了双膦酸盐帕米膦酸（PAM）和唑来膦酸（ZOL）对原代人成骨细胞（hOB）中OPG mRNA稳态水平（通过半定量RT-PCR）和蛋白质产生（通过ELISA）的影响。PAM以剂量依赖性方式使hOB的OPG mRNA水平和蛋白质分泌增加高达2至3倍，在72小时后10(-6) M时达到最大效应（P < 0.001）。同样，ZOL以剂量依赖性方式增强hOB的OPG基因表达和蛋白质分泌，在72小时后10(-8) M时达到最大效应，这与ZOL更高的生物学活性一致。时间进程实验表明，PAM和ZOL分别使成骨细胞OPG蛋白质分泌增加6倍（P < 0.001）。用PAM和ZOL预处理可防止糖皮质激素地塞米松对OPG mRNA和蛋白质产生的抑制作用。对成骨细胞分化的细胞标志物分析显示，PAM和ZOL分别使I型胶原蛋白分泌和碱性磷酸酶活性增加2倍和4倍（方差分析P < 0.0001）。总之，我们的数据表明双膦酸盐可调节正常人成骨细胞中OPG的产生，这可能有助于抑制破骨细胞性骨吸收。由于OPG的产生随着成骨细胞的成熟而增加，双膦酸盐对OPG的增强作用可能与其对成骨细胞分化的刺激作用有关。
