Traumatic Axonopathy in the CNS as Wallerian degeneration

项目摘要 在本申请中，我们提出创伤性轴索损伤（TAI）导致活动性轴索病， 沃勒变性的特征，靶向一些相关信号可以保护轴突， 大脑系统这一假设是基于我们实验室最近的发现， 扩散性TAI后依赖于无菌α和含TIR基序1（SARM 1）信号传导的激活， 阻断SARM 1的分子干预在保护轴突和拯救神经元方面取得了重大进展， 依赖轴突完整性的功能/行为。TAI的情况是独特的，因为许多轴突 只有部分受伤，可能是可以挽救的，因此阻止沃勒式自毁可能 提供长期的神经保护并改变创伤性脑损伤的预后。我们的建议是有组织的 三个具体目标。在目的1中，我们确定了在指标CNS道（即皮质脊髓系统）中的TAI导致 进行性轴突病与沃勒变性的分子特征，即SARM 1的激活。在 目的2：我们想知道是否通过遗传或药物阻断SARM 1信号通路来保护轴突， 损伤的皮质脊髓束转化为系统水平的保护，即预防皮质脊髓束的逆行性萎缩。 皮质脊髓神经元，保留皮质脊髓连接和CST依赖性运动技能的拯救。在 目的3探讨丝裂原活化蛋白激酶（MAPK）通路在细胞凋亡中的协同作用， 在皮质脊髓轴突中通过双亮氨酸拉链激酶（DLK）和相关亮氨酸拉链激酶（LZK）的信号传导， TAI后退化。MAPK通路信号传导对损伤的一般神经元反应，并且存在 证据表明，通路的特定成员与SARM 1相关信号合作，触发或影响 沃勒变性的结果为了实现上述目标，我们使用了分子的补充， 基因工具，包括基因敲除小鼠、显性阴性策略和CRISPR-Cas9基因组编辑， 代谢组学评估、基于能量的高分辨率神经病理学、结构和功能 连接标记物、行为测试和小分子作为分子靶标的探针， 治疗剂（NAMPT抑制剂FK 866，其用作SARM 1的间接抑制剂，以及泛Aurora抑制剂）， 阻断DLK/LZK信号传导的抑制剂tozasertib）。总之，在这里，我们探索特定的分子机制， 与沃勒变性有关，在此过程中，我们建立了潜在的分子靶点， 创伤性脑损伤的药物干预。

PROJECT SUMMARY In this application we propose that traumatic axonal injury (TAI) leads to an active axonopathy with the molecular features of Wallerian degeneration and that targeting some of the relevant signals may protect axons as well as brain systems. This hypothesis is based on recent findings in our laboratory showing that axonal breakdown after diffuse TAI depends on the activation of Sterile Alpha and TIR Motif Containing 1 (SARM1) signaling and that molecular interventions to block SARM1 lead to significant gains in preserving axons and rescuing functions/behaviors that rely on axonal integrity. The case of TAI is unique in the sense that that many axons are only partially injured and are potentially salvageable, therefore blocking Wallerian-type self-destruction may afford long-term neuroprotection and change the prognosis of traumatic brain injury. Our proposal is organized in three specific aims. In Aim 1 we establish that TAI in an index CNS tract, i.e. the corticospinal system, leads to progressive axonopathy with the molecular signatures of Wallerian degeneration, i.e. activation of SARM1. In Aim 2 we ask whether axonal protection by genetic or pharmacological blockade of SARM1 signaling in the injured corticospinal tract translate into protection at the systems level, i.e. prevention of retrograde atrophy of corticospinal neurons, preservation of corticospinal connectivity and rescue of CST-dependent motor skills. In Aim 3 we explore the synergistic role of the mitogen-activated protein kinase (MAPK) pathway, specifically signaling by the dual leucine zipper kinase (DLK) and related leucine zipper kinase (LZK), in corticospinal axonal degeneration following TAI. The MAPK pathway signals general neuronal responses to injury and there is evidence that specific members of the pathway cooperate with SARM1-related signals in triggering or affecting the outcome of Wallerian degeneration. To achieve the previous aims, we use a complement of molecular genetic tools including knockout mice, dominant negative strategies and genome editing with CRISPR-Cas9, metabolomic assessments, CLARITY-based high-resolution neuropathology, structural and functional connectivity markers, behavioral testing, and small molecules as probes for molecular targets and also as therapeutic agents (the NAMPT inhibitor FK866 that serves as indirect inhibitor of SARM1 and the pan-Aurora inhibitor tozasertib that blocks DLK/LZK signaling). In summary, here we explore specific molecular mechanisms related to Wallerian degeneration and, in the course of doing this, we establish molecular targets for potential pharmacological interventions in traumatic brain injury.