Zoledronic acid up-regulates bone sialoprotein expression in osteoblastic cells through Rho GTPase inhibition
Zoledronic acid up-regulates bone sialoprotein expression in osteoblastic cells through Rho GTPase inhibition
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DOI：
10.1042/bj20040380
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发表时间：
2004-12-15
影响因子：
4.1
通讯作者：
Bellahcène, A
中科院分区：
文献类型：
--
作者：
Chaplet, ML;Detry, D;Bellahcène, A
临床实践表明，用BPs（双膦酸盐）治疗的女性骨质疏松症显示出骨密度增加和骨折风险降低。然而，导致BPs这些有益作用的机制仍然知之甚少。我们假设，ZOL（唑来膦酸），一种有效的第三代BP，可能会诱导与成骨细胞的骨形成潜力相关的蛋白质的表达，如BSP（骨唾液酸蛋白）。BSP基因的表达受促进骨形成的激素上调，并与从头骨矿化有关。利用实时荧光定量RT-PCR和Western-blot分析，我们证明ZOL增加了BSP在Saos-2成骨样细胞中的表达。核运行和mRNA衰变分析表明，在转录水平上没有影响，但稳定的BSP转录ZOL处理的细胞。ZOL对BSP表达的影响通过干扰甲羟戊酸途径发生，因为它被甲羟戊酸途径中间体或Rho GT3激活剂逆转。我们发现，ZOL损害膜定位的RhoA在Saos-2细胞表明减少异戊二烯化的这种蛋白质。通过使用针对RhoA和Rac 1的小干扰RNA，我们鉴定了两种Rho GTP酶作为Saos-2细胞中BSP表达的负调节因子。我们的研究表明，ZOL诱导BSP表达成骨细胞样细胞通过灭活Rho GTP酶，并提供了一个潜在的机制来解释ZOL治疗对骨量和完整性的有利影响。
Clinical practice reveals that osteoporotic women treated with BPs (bisphosphonates) show an increased bone mass density and a reduced risk of fractures. However, the mechanisms leading to these beneficial effects of BPs are still poorly understood. We hypothesized that ZOL (zoledronic acid), a potent third-generation BP, may induce the expression of proteins associated with the bone-forming potential of osteoblastic cells such as BSP (bone sialoprotein). Expression of BSP gene is up-regulated by hormones that promote bone formation and has been associated with de novo bone mineralization. Using real-time reverse transcriptase-PCR and Western-blot analysis, we demonstrated that ZOL increased BSP expression in Saos-2 osteoblast-like cells. Nuclear run-on and mRNA decay assays showed no effect at the transcriptional level but a stabilization of BSP transcripts in ZOL-treated cells. ZOL effect on BSP expression occurred through an interference with the mevalonate pathway since it was reversed by either mevalonate pathway intermediates or a Rho GTPase activator. We showed that ZOL impaired membrane localization of RhoA in Saos-2 cells indicating reduced prenylation of this protein. By the use of small interfering RNAs directed to RhoA and Rac1, we identified both Rho GTPases as negative regulators of BSP expression in Saos-2 cells. Our study demonstrates that ZOL induces BSP expression in osteoblast-like cells through inactivation of Rho GTPases and provides a potential mechanism to explain the favourable effects of ZOL treatment on bone mass and integrity.