GLUOCORTICOIDS, OSTEOCYTES, BONE STENGTH IN AGE-RELATED

糖皮质激素、骨细胞、年龄相关的骨强度

• 批准号: 7094998
• 负责人: ROBERT Stewart WEINSTEIN
• 金额: $ 17.14万
• 依托单位: UNIV OF ARKANSAS FOR MED SCIS
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-06-01 至 2011-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7094998
• 关键词: Mus musculus; aging; apoptosis; biomechanics; bone density; bone fracture; cellular pathology; extracellular matrix proteins; focal adhesion kinase; genetically modified animals; glucocorticoids; molecular pathology; osteoblasts; osteoclasts; osteocytes; osteoporosis; prednisolone; skeletal pharmacology

Based on the discovery that glucocorticoid-induced loss of bone strength results in part from increased death of osteocytes independent of bone loss, and evidence that cortisol levels as well as local tissue amplification of glucocorticoid action increase with age in both mice and humans, the hypothesis that the disparity between bone strength and mass that occurs with aging is due in part to the adverse skeletal impact of endogenous glucocorticoids will be tested. This enhancement of glucocorticoid effects would result in an increase in the prevalence of osteocyte apoptosis and prolongation of osteoclast lifespan. Glucocorticoid effects on these cells result from nongenotropic mechanisms involving proline-rich tyrosine kinase 2 (Pyk2) activation. The ensuing glucocorticoid-induced osteocyte apoptosis negatively affects bone strength by disrupting canalicular circulation, degrading material properties, allowing accumulation of damaged bone, or all three. To test this hypothesis, in Aim 1, the contrast in vivo between the loss of bone mineral density (BMD) and strength at 8, 16, and 25 months of age in wild-type and transgenic mice overexpressing 113-hydroxysteroid dehydrogenase type 2, an enzyme that inactivates glucocorticoids in a pre-receptor fashion, will be determined. This will be accomplished either under the control of the osteocalcin promoter (thus protecting osteocytes and osteoblasts from glucocorticoid action) or under control of the tartrate-resistant acid phosphatase promoter (thus protecting osteoclasts from glucocorticoid actions). In Aim 2, the role of the focal adhesion-related protein Pyk2 in the opposing effects of glucocorticoids on osteocyte and osteoclast lifespan will be delineated. Specifically, those opposing effects are the induction of osteocyte apoptosis and prevention of osteoclast apoptosis. In Aim 3, the contribution of osteocyte apoptosis to bone strength will be determined by inducing rapid, conditional osteocyte ablation via apoptosis using diphtheria toxin administration and the dentin matrix protein 1 promoter controlling the diphtheria toxin receptor in mice, an otherwise diphtheria toxin-insensitive species. The innovative studies proposed in this project will extend previous work by delineating the contribution of endogenous glucocorticoids to the multifactorial damages that affect the aging skeleton. The importance of this project is amplified by the increasing burden of osteoporosis that will occur with the aging of America. Older people are more sensitive to the adverse skeletal effects of glucocorticoids and this project will provide a detailed investigation of how the glucocorticoids produced by their adrenal glands contribute to fractures in the agjng skeleton.

基于以下发现：糖皮质激素引起的骨强度损失部分是由于骨强度增加所致 骨细胞死亡与骨质流失无关，并且有证据表明皮质醇水平以及局部组织 在小鼠和人类中，糖皮质激素作用随着年龄的增长而增强，假设 随着衰老而出现的骨强度和质量之间的差异部分是由于骨骼的不利影响 将测试内源性糖皮质激素的影响。糖皮质激素作用的增强将 导致骨细胞凋亡发生率增加和破骨细胞寿命延长。 糖皮质激素对这些细胞的作用是由涉及富含脯氨酸的酪氨酸的非致基因机制引起的 激酶 2 (Pyk2) 激活。随后的糖皮质激素诱导的骨细胞凋亡对骨产生负面影响 通过扰乱小管循环、降低材料性能、允许积累来增强强度 骨头受损，或三者皆有。为了检验这一假设，在目标 1 中，骨损失与骨质流失之间的体内对比 野生型和转基因小鼠 8、16 和 25 月龄时的矿物质密度 (BMD) 和强度 过度表达 2 型 113-羟基类固醇脱氢酶，一种使糖皮质激素失活的酶 预受体时尚，将被确定。这将在以下机构的控制下完成： 骨钙素促进剂（从而保护骨细胞和成骨细胞免受糖皮质激素的作用）或低于 控制抗酒石酸酸性磷酸酶启动子（从而保护破骨细胞免受糖皮质激素的影响） 行动）。在目标 2 中，粘着斑相关蛋白 Pyk2 在相反作用中的作用 糖皮质激素对骨细胞和破骨细胞寿命的影响将被描述。具体来说，那些相反的影响 是诱导骨细胞凋亡和预防破骨细胞凋亡。在目标 3 中，贡献 骨细胞凋亡对骨强度的影响将通过诱导快速、有条件的骨细胞消融来确定 通过使用白喉毒素施用和控制牙本质基质蛋白 1 启动子的细胞凋亡 小鼠体内的白喉毒素受体，是一种对白喉毒素不敏感的物种。创新研究 该项目中提出的建议将通过描述内生的贡献来扩展以前的工作 糖皮质激素可减轻影响骨骼老化的多因素损伤。这个项目的重要性在于 随着美国老龄化，骨质疏松症的负担日益加重，这一情况更加严重。老年人 对糖皮质激素对骨骼的不利影响更敏感，该项目将提供详细的 研究肾上腺产生的糖皮质激素如何导致老年骨折 骨骼。