Differential Impact of Resveratrol and Resveratrol Mimetics Upon Aging Bone

描述(由申请人提供)： 骨质疏松症是老年人虚弱、发病率增加和死亡率增加的普遍因素，是骨吸收和骨形成之间失衡的结果。Sirtuins被认为与新陈代谢、长寿和健康有关。白藜芦醇(RSV)是一种sirtuin激活化合物，可提高小鼠的骨密度(BMD)，sirtuin基因敲除小鼠显示出更多的破骨细胞生成。SRT2183和SRT1720是人工合成的白藜芦醇模拟物(SyRms)，专为激活Sirt1(Sirt1)而设计，但越来越多的报告表明RSV和SyRms作用于Sirt1以外的靶点。我们的初步数据表明：1)SyRms抑制c-Src磷酸化，肌动蛋白环的形成，破骨细胞的形成和骨吸收，但RSV没有；2)SyRms也破坏成熟破骨细胞的肌动蛋白环并抑制骨吸收，但RSV没有；3)敲除Sirt1表达基因后，体内的骨质量下降，体外的破骨细胞生成增加，但SyRms仍然抑制Sirt1基因敲除细胞的肌动蛋白环和破骨细胞的形成；4)RSV对幼年小鼠的治疗增加成骨细胞，减少破骨细胞的形成；5)对极老年小鼠的RSV治疗显著改善骨量和骨质量。假设和特定目的：我们假设SyRms抑制破骨细胞形成和功能的关键途径，涉及c-Src磷酸化、Rho GTPase激活和NFATc1表达。有趣的是，尽管在体外缺乏作用，但RSV在体内发挥了显著的益处，表明主要作用是对成骨细胞。我们认为，RSV和SyRms体内治疗都可以恢复年轻时破骨细胞性骨吸收和成骨细胞性骨形成之间的平衡，并提高骨密度和骨质量，但可能是通过不同的机制。我们还假设，Syrms可以独立于Sirt1对骨骼产生有益的影响。1.确定RSV、RSV模拟物和Sirt1调控破骨细胞和成骨细胞形成的机制。这一目标的结果将回答以下关键问题：SyRms是否通过抑制c-Src磷酸化、Rho GTPase激活和NFATc1表达来抑制破骨细胞的生成，以及SyRms的作用是否依赖于Sirt1。2.确定RSV、RSV模拟物和Sirt1在体内对骨骼的影响。这一目标的结果将回答以下关键问题：在体内RSV和SyRMs是否可以防止年龄相关和/或卵巢切除引起的骨丢失，RSV和SyRms是否对骨发挥合成代谢和抗吸收作用，以及RSV和SyRms的影响是否取决于Sirt1基因的表达。迫切需要有针对性的药物来改善骨骼质量，减少骨质疏松症的不良后果。我们提出的研究将使我们能够更好地理解RSV和SyRMS影响的机制(S)及其与Sirt1表达的关系。鉴于老年人普遍存在的骨质疏松的有害负担，我们的工作也将对临床产生重大影响，并可应用于RSV和RSV模拟物的临床应用。 公共卫生相关性： 骨质疏松症是由骨吸收和骨形成之间的失衡引起的，导致进行性骨丢失、骨折，并增加老年人的发病率和死亡率。我们发现合成的白藜芦醇类似物(SyRms)可以抑制Rho GTP酶的激活、NFATc1的表达、肌动蛋白环的形成以及破骨细胞的形成和吸收。我们假设SyRms既是合成代谢的，又是抗吸收的，因此可以恢复年轻时骨吸收和形成之间的平衡。我们将通过研究白藜芦醇和Syrms在衰老过程中对骨骼的细胞影响以及在绝经期骨丢失的小鼠模型中来验证这一假设。通过利用成骨细胞或破骨细胞中sirtuin基因敲除的小鼠，我们还将评估这些影响是否依赖于sirtuin的表达。我们提出的实验数据可以应用于骨质疏松症新疗法的开发。

DESCRIPTION (provided by applicant): Osteoporosis is a widely prevalent contributor to frailty, increased morbidity, and mortality in the elderly and results from an imbalance between bone resorption and bone formation. Sirtuins have been implicated in metabolism, longevity, and healthspan. Resveratrol (RSV) is a sirtuin activating compound that enhances bone mineral density (BMD) in mice, and sirtuin knockout mice exhibit increased osteoclastogenesis. SRT2183 and SRT1720 are synthetic resveratrol mimetics (SyRMs) that were designed to specifically activate sirtuin1 (Sirt1), but an increasing number of reports suggest that RSV and SyRMs act on targets other than Sirt1. Our preliminary data demonstrate that: 1) SyRMs inhibit c-Src phosphorylation, actin ring formation, osteoclast formation, and bone resorption, but RSV does not; 2) SyRMs also disrupt actin rings and inhibit bone resorption in mature osteoclasts, but RSV does not; 3) knockout of Sirt1 expression impairs bone quality in vivo and enhances osteoclastogenesis ex vivo, but SyRMs still inhibit actin ring and osteoclast formation in Sirt1 knockout cells; 4) RSV treatment of young mice increases osteoblastogenesis and decreases osteoclastogenesis; and 5) RSV treatment of very old mice markedly improves bone mass and bone quality. Hypothesis and Specific Aims: We hypothesize that SyRMs inhibit critical pathways of osteoclast formation and function involving c-Src phosphorylation, Rho GTPase activation, and NFATc1 expression. Intriguingly, despite lack of effect in vitro, RSV exerts pronounced benefit in vivo, suggesting that the predominant effects are on osteoblasts. We propose that in vivo treatment with RSV and SyRMs will both restore the youthful balance between osteoclastic bone resorption and osteoblastic bone formation and enhancing bone mineral density and bone quality, but possibly via different mechanisms. We also hypothesize that the SyRMs can exert beneficial effects upon bone independent of Sirt1. 1. Determine the mechanisms whereby RSV, RSV mimetics, and Sirt1 regulate osteoclast and osteoblast formation. The results of this aim will answer the critical questions of whether or not SyRMs inhibit osteoclastogenesis by inhibiting c-Src phosphorylation, Rho GTPase activation, and NFATc1 expression and whether the effects of SyRMs depend upon Sirt1. 2. Determine the skeletal impacts of RSV, RSV mimetics, and Sirt1 in vivo. The results of this aim will answer the critical questions of whether or not in vivo RSV and SyRMs prevent age-related and/or ovariectomy-induced bone loss, whether RSV and SyRMs exert either anabolic and anti-resorptive effects on bone or both, and whether the impacts of RSV and SyRMs depend upon Sirt1 gene expression. There is a pressing need for targeted agents to improve the quality of bone and to reduce the adverse consequences of osteoporosis. Our proposed studies will permit us to understand better the mechanism(s) underlying the impacts of RSV and SyRMs and their relationship to Sirt1 expression. Our work will also have significant clinical impact given the widespread and deleterious burden of osteoporosis in the elderly and can be applied to the utilization of RSV and RSV mimetics in the clinic. PUBLIC HEALTH RELEVANCE: Osteoporosis results from an imbalance between bone resorption and bone formation leading to progressive bone loss, fractures, and increased morbidity and mortality in the elderly. We have found that synthetic resveratrol mimetics (SyRMs) inhibit Rho GTPase activation, NFATc1 expression, actin ring formation, and osteoclast formation and resorption. We hypothesize that SyRMs are both anabolic and anti-resorptive and can therefore restore the youthful balance between bone resorption and formation. We will test this hypothesis by studying the cellular impacts of resveratrol and SyRMs on bone during aging and in a mouse model of menopausal bone loss. By utilizing mice with knockout of the sirtuin gene in either osteoblasts or osteoclasts, we will also assess whether these impacts depend upon sirtuin expression. The data derived from our proposed experiments can be applied to the development of new treatments for osteoporosis.