Bone neuro-mechanosignaling and inflammation: New players in diabetic osteopenia

项目摘要 骨丢失是一种糖尿病并发症，经常被忽视，其潜在机制仍不清楚 很好理解。我们提出骨细胞Panx 1-P2 X7 R机械信号调节的改变 复合物破坏了适当的负荷诱导的骨适应，并可能导致1型糖尿病的骨丢失 （T1D）。然而，负荷诱导的骨量调节不仅发生在局部骨水平， 包括骨骼和神经系统之间的直接信号传递。糖尿病影响神经系统， 特别是感觉神经，然而，糖尿病损害负荷诱导的神经调节的程度 骨反应仍然未知。我们的研究表明，除了在骨细胞机械信号中的作用外， Panx 1-P2 X7 R还参与骨神经机械感觉信号传导，并介导负荷诱导的骨损伤。 炎症体激活，这两个新功能也是糖尿病的目标。神经营养素减少 神经生长因子是糖尿病周围神经病变的标志。NGF及其TrkA受体是 骨神经机械感觉系统的组成部分。负荷诱导的成骨细胞释放NGF已经被证实是一种重要的生物学效应。 提出在骨感觉纤维中启动NGF-TrkA信号传导，这对于负荷诱导的骨是必不可少的 在小鼠中形成。我们的初步数据表明，NGF-TrkA信号在T1 D秋田骨中减弱， 通过骨骼和支配后肢的背根神经节（DRG）中较低的NGF水平证明。并且我们在 观察到负荷调节NGF-TrkA信号成分的表达，这是一种在T1 D中丢失的反应， 骨头这一发现表明，糖尿病破坏了骨机械感觉的神经轴， 系统，从而损害骨形成的负荷诱导调节的神经成分。此外，本发明还提供了一种方法， 背根神经节中负荷诱导的Panx 1-P2 X7 R上调的发现表明其参与了 调节骨感觉神经元兴奋性。炎症与骨质流失有关。炎性细胞因子 在小鼠T1 D的早期阶段， 用于诱导糖尿病性骨丢失。我们的初步数据表明，在T1 D患者中， 秋田，这与Panx 1-P2 X7 R失调和炎性小体激活相一致。荷载引起的燃烧 糖尿病骨中的炎症可能由已知的NLRP 3炎性体激活剂Panx 1-P2 X7 R驱动。 根据我们的初步资料，我们提出：（1）糖尿病周围神经病变有助于病因， 糖尿病骨质减少通过影响骨感觉纤维和改变负荷诱导骨的神经调节 （2）Panx 1-P2 X7 R不仅在骨中，而且在DRG中的调节对于负荷诱导的骨形成是必需的。 反应和骨骼适应，和（3）负荷诱导的糖尿病骨中Panx 1-P2 X7 R的失调 增强局部炎症反应，导致骨合成代谢反应受损。测试这些 假设我们将使用T1 D小鼠模型，胰岛素治疗，时间序列加载，分子，生物化学， 组织形态学、药理学和遗传学方法。这些研究将确立以下方面的重要性： 骨神经机械信号传导和炎症作为糖尿病骨质减少的新参与者，并确定新的 Panx 1-P2 X7 R功能复合物在健康和疾病中调节骨适应的关键作用。

Project Summary Bone loss is a diabetic complication that is often overlooked and the underlying mechanisms are still not well understood. We have proposed that altered regulation of the osteocyte Panx1-P2X7R mechanosignaling complex disrupts proper load-induced bone adaptation and likely contributes to bone loss in Type 1 diabetes (T1D). However, load-induced regulation of bone mass occurs not only at the local bone level but remotely involving direct signaling between the bone and the nervous system. Diabetes affects the nervous system, particularly sensory nerves and yet, the extent to which diabetes impairs neural regulation of load-induced bone responses is still unknown. Our studies indicate that besides its role in osteocytic mechanosignaling, Panx1-P2X7R also participates in bone neuro-mechanosensory signaling and mediates load-induced inflammasome activation, two new functions that are also targeted by diabetes. Reduction in neurotrophic factors, mainly NGF, is a hallmark of diabetic peripheral neuropathy. NGF and its TrkA receptor are components of the bone neuro-mechanosensory system. Load-induced NGF release from osteoblast has been proposed to initiate NGF-TrkA signaling in bone sensory fibers that is essential for load-induced bone formation in mice. Our preliminary data indicates that NGF-TrkA signaling is attenuated in T1D Akita bones, as evidenced by lower NGF levels in bone and dorsal root ganglia (DRG) innervating the hind limbs. Moreover we observed that loading regulates expression of NGF-TrkA signaling components, a response that is lost in T1D bones. This finding suggests that diabetes disrupts the neurosensory axis of the bone mechanosensory system, thereby impairing the neural component of the load-induced regulation of bone formation. In addition, findings of load-induced Panx1-P2X7R upregulation in DRG suggest its participation in mechanisms that modulate bone sensory neurons excitability. Inflammation is associated with bone loss. Inflammatory cytokines are shown to be increased in bones at early stages of T1D in mice, which has been proposed to be necessary for induction of diabetic bone loss. Our preliminary data indicates that loading worsens inflammation in T1D Akita, which coincides with Panx1-P2X7R dysregulation and inflammasome activation. Load-induced flaring of inflammation in diabetic bone is likely driven by Panx1-P2X7R, known activators of NLRP3 inflammasome. Based on our preliminary data, we propose that (1) diabetic peripheral neuropathy contributes to the etiology of diabetic osteopenia by affecting the bone sensory fibers and altering neural regulation of load-induced bone formation; (2) Panx1-P2X7R regulation not only in the bone but also in the DRG is essential for load-induced responses and skeletal adaptation, and (3) load-induced dysregulation of Panx1-P2X7R in diabetic bone augments local inflammatory responses that contribute to impair bone anabolic responses. To test these hypotheses we will use T1D mouse models, insulin therapy, time series loading, molecular, biochemical, histomorphometric, pharmacological and genetic approaches. These studies will establish the importance of bone neuro-mechanosignaling and inflammation as new players in diabetic osteopenia and identify novel and critical roles for the Panx1-P2X7R functional complex in regulation of bone adaptation in health and disease.