Osteocyte apoptosis and regulation of bone resorption with aging

衰老过程中骨细胞凋亡和骨吸收的调节

• 批准号: 9308117
• 负责人: Lilian Irene Plotkin
• 金额: $ 9.79万
• 依托单位: INDIANA UNIV-PURDUE UNIV AT INDIANAPOLIS
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2020-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9308117
• 关键词: Advanced Glycosylation End Products; Aging; Animals; Apoptosis; Apoptotic; Architecture; Area; Bone Resorption; CASP6 gene; Caspase; Cell Death; Cell Survival; Cells; Chemotactic Factors; Connexin 43; Connexins; Cytoplasmic Tail; Development; Duct (organ) structure; Effectiveness; Event; Excision; Exhibits; Gap Junctions; Genetic; Goals; HMGB1 Protein; Human; In Vitro; Individual; Intervention; Lead; Length; Link; Mediating; Mediator of activation protein; MicroRNAs; Mission; Molecular; Mus; Osteoclasts; Osteocytes; Pharmacology; Phenotype; Phosphotransferases; Play; Prevalence; Property; Public Health; Receptor Activation; Recruitment Activity; Regulation; Role; Signal Pathway; Signal Transduction; Skeleton; Surface; Syndrome; System; TLR4 gene; TNFSF11 gene; Tertiary Protein Structure; Testing; Tumor necrosis factor receptor 11b; United States National Institutes of Health; Wild Type Mouse; Work; age effect; bone; bone fragility; bone loss; cortical bone; cytokine; improved; in vivo; inhibitor/antagonist; mouse model; novel; overexpression; permissiveness; prevent; public health relevance; receptor; scaffold; skeletal; Advanced Glycosylation End Products; Aging; Animals; Apoptosis; Apoptotic; Architecture; Area; Bone Resorption; CASP6 gene; Caspase; Cell Death; Cell Survival; Cells; Chemotactic Factors; Connexin 43; Connexins; Cytoplasmic Tail; Development; Duct (organ) structure; Effectiveness; Event; Excision; Exhibits; Gap Junctions; Genetic; Goals; HMGB1 Protein; Human; In Vitro; Individual; Intervention; Lead; Length; Link; Mediating; Mediator of activation protein; MicroRNAs; Mission; Molecular; Mus; Osteoclasts; Osteocytes; Pharmacology; Phenotype; Phosphotransferases; Play; Prevalence; Property; Public Health; Receptor Activation; Recruitment Activity; Regulation; Role; Signal Pathway; Signal Transduction; Skeleton; Surface; Syndrome; System; TLR4 gene; TNFSF11 gene; Tertiary Protein Structure; Testing; Tumor necrosis factor receptor 11b; United States National Institutes of Health; Wild Type Mouse; Work; age effect; bone; bone fragility; bone loss; cortical bone; cytokine; improved; in vivo; inhibitor/antagonist; mouse model; novel; overexpression; permissiveness; prevent; public health relevance; receptor; scaffold; skeletal

DESCRIPTION (provided by applicant): Aging of the skeleton is associated with increased prevalence of osteocyte apoptosis in mice and humans. Work leading to this application shows that the skeletal syndrome that ensues with aging is mimicked by osteocyte specific deletion of the gap junction protein connexin (Cx) 43. Mice lacking Cx43 in osteocytes exhibit increased osteocyte apoptosis and accumulation of empty lacunae, and reduced OPG levels, and Cx43- deficient osteocytes express lower levels of the survival-associated microRNA (miR) miR21. In addition, bones from old mice exhibit reduced Cx43, OPG, and miR21 expression. We showed in vitro that apoptotic osteocytes release high mobility group box protein1 (HMGB1), which reduces OPG expression and increases osteoclast recruitment and differentiation through activation of receptors for advanced glycation end products (RAGE). HMGB1 also activated toll-like receptor 4 (TLR4). However, whether activation of HMGB1 receptors RAGE or TLR4 has a role in the skeletal phenotype of Cx43-deficient or old mice is not known. The mechanism by which HMGB1 is released by apoptotic cells is not known. A potential mechanism could involve opening of Pannexin1 (Pax1) channels in cells undergoing apoptosis. Whether this mechanism operates in osteocytes undergoing apoptosis is not known. The long-term goal of our studies is to improve the management of the adverse skeletal effects of aging by targeting osteocyte apoptosis and resorption. The specific objective of this application is to define the signaling pathways involved in the elevated osteocyte apoptosis and bone resorption in aging. We propose that the bone fragility syndrome that ensues with aging is due to increased osteocyte apoptosis as a consequence of reduced expression of osteocytic Cx43, OPG, and miR21. We hypothesize that low OPG and the consequent increase in the RANKL/OPG ratio acts as a permissive event for osteoclast development; whereas low miR21 reduces anti-apoptotic kinase signaling and activates caspases, with the consequent Panx1 channel opening and HMGB1 release, directing osteoclasts to areas with accumulated apoptotic osteocytes. To test this hypothesis, we will pursue a combination of in vivo and in vitro studies that include the use of novel genetically modified mice, and established and primary osteocytic cells. Aim 1 will examine the role of Cx43/miR21 on osteocyte apoptosis with aging. Aim 2 will investigate the role of HMGB1 in osteoclast recruitment and differentiation in Cx43 deficiency and aging. Aim 3 will explore the consequence of osteocytic Panx1 removal on HMGB1 release and osteoclast recruitment. Successful completion of these studies will provide the molecular basis for the in- creased osteocyte apoptosis in the absence of Cx43 and in old animals. In addition, these studies will establish the molecular link between dying osteocytes and targeted bone resorption. Moreover, they will offer the basis for treatments in which the effect of increased osteocyte apoptosis on osteoclast recruitment are counteracted by targeting the HMGB1-RAGE/TLR4 system.

描述（由申请人提供）：骨骼的衰老与小鼠和人类骨细胞凋亡的患病率增加有关。导致该应用的工作表明，随着衰老而随之而来的骨骼综合征通过骨细胞的特异性缺失模仿间隙连接蛋白连接素（CX）43。在骨细胞中缺乏CX43缺乏CX43的小鼠表现出增加的骨细胞的骨质细胞增长和较低级别的lacuneae和lacunae级别的lacuneae和cox的水平，并延迟了。与生存相关的microRNA（miR）mir21的此外，旧小鼠的骨骼表现出降低的CX43，OPG和MIR21表达。我们在体外表明，凋亡的骨细胞释放高迁移率组盒蛋白1（HMGB1），从而降低了OPG表达，并通过激活高级糖化终端产物（RAGE）的受体来减少OPG表达并增加破骨细胞的募集和分化。 HMGB1还激活了Toll样受体4（TLR4）。但是，HMGB1受体愤怒还是TLR4是否在CX43缺陷型或旧小鼠的骨骼表型中起作用。凋亡细胞释放HMGB1的机制尚不清楚。潜在的机制可能涉及在经历凋亡的细胞中开放Pannexin1（PAX1）通道。该机制是否在凋亡的骨细胞中起作用，尚不清楚。我们研究的长期目标是通过靶向骨细胞凋亡和吸收来改善衰老不良骨骼影响的管理。该应用的具体目的是定义与衰老中骨细胞凋亡和骨吸收升高有关的信号传导途径。我们建议随着衰老而随之而来的骨脆性综合征是由于骨细胞CX43，OPG和MIR21的表达降低而导致的骨细胞凋亡增加。我们假设较低的OPG和RANKL/OPG比率的增加是破骨细胞发育的允许事件。低miR21降低了抗凋亡激酶信号传导并激活胱天蛋白酶，随之而来的Panx1通道开口和HMGB1释放，将破骨细胞引导到具有积累的凋亡骨细胞的区域。为了检验这一假设，我们将追求体内和体外研究的组合，其中包括使用新型遗传修饰的小鼠以及已建立和原发性骨细胞细胞。 AIM 1将检查CX43/MIR21在衰老中的骨细胞凋亡中的作用。 AIM 2将研究HMGB1在CX43缺乏症和衰老中的破骨细胞募集和分化中的作用。 AIM 3将探讨骨细胞PANX1在HMGB1释放和破骨细胞募集中的去除的后果。这些研究的成功完成将为在没有CX43和旧动物中的骨细胞凋亡提供分子基础。此外，这些研究将在垂死的骨细胞和靶向骨吸收之间建立分子联系。此外，他们将通过针对HMGB1-RAGE/TLR4系统来抵消骨细胞凋亡对骨细胞募集的影响的治疗基础。