Therapeutic benefit of targeting neuroinflammation in spinal cord injury with a novel small molecule inhibitor of the RNA regulator HuR

脊髓损伤（SCI）是毁灭性的，最常影响年轻的退伍军人。长期存在重大 发病率高，寿命短，经济负担重。由于再生能力差， 脊髓，发展早期干预措施，尽量减少继发性组织损伤是一个优先事项。一个主要 炎症级联反应是继发性组织损伤和神经病理性疼痛起始的原因 由激活的神经胶质细胞（小胶质细胞和星形胶质细胞）触发。这种级联反应在SCI后立即开始， 细胞因子、反应性物质和血管活性物质的释放。这种分泌蛋白质组对 神经元，少突胶质细胞和其他细胞在和超越损伤水平，通过直接细胞毒性 机制或间接通过促进细胞毒性和血管源性水肿，血管妥协， 组织缺血这些炎症介质也会触发导致慢性疼痛的途径。的 神经胶质细胞产生趋化因子进一步加速炎症级联反应，趋化因子募集外周免疫 细胞，包括中性粒细胞和单核细胞，在损伤的急性期。最初的神经胶质细胞的主要驱动力 反应是HuR，一种RNA调节剂，通过调节炎症介质的表达来促进关键炎症介质的表达。 转录后机制炎症介质如IL-1β、IL-6、TNF-α和iNOS含有 HuR与3'非翻译区（ARE）结合并呈阳性的富含腺嘌呤和尿苷的元件 调节其表达。我们先前在SCI中的工作表明，HuR在SCI的急性期被激活， 当在神经胶质细胞中过度表达时会加重损伤。我们的团队开发了一类新型的小分子HuR 阻断神经胶质细胞中炎症介质诱导的抑制剂。在一项使用中- 胸部挫伤模型，我们观察到临床缺陷和神经元丢失的衰减与原型HuR 抑制剂，SRI-42127。我们还发现，SRI-42127减少了外周神经损伤模型中的异常性疼痛。 在这个提议中，我们假设HuR驱动促炎和毒性分泌蛋白的表达， 在SCI的早期阶段触发的常驻胶质细胞，抑制HuR将减少 继发性组织损伤，改善运动结果和减少神经性疼痛。我们提出三个具体的 目的：（1）进一步表征SRI-42127抑制HuR对SCI恢复的有益作用，（2）评估 HuR抑制改善SCI后恢复的机制，以及（3）评估胶质HuR的贡献 炎症反应和组织损伤。本提案的长期目标是促进 我们的小分子HuR抑制剂作为急性SCI的治疗方法，并获得如何机制的理解， ARE介导的转录后调节影响SCI（继发性组织损伤，运动恢复和 神经性疼痛）。这一提议的创新之处在于研究了一类新型的HuR抑制剂， 针对SCI急性炎症反应的治疗和SCI后炎症反应的机制研究 转录途径（迄今基本上未探索）在SCI。这一应用的意义在于其 专注于一种治疗方法，这种方法最终可能在战场上使用， 临床前研究表明，SRI-42127极好且快速地渗透到中枢神经系统中， 外周给药，以及对神经元损失和神经性疼痛的缓解作用。意义 在其他急性CNS中，同样的HuR调节通路驱动神经炎症， 损伤（例如创伤性脑损伤或中风）和慢性神经系统疾病（例如ALS和阿尔茨海默氏症）。

Spinal cord injury (SCI) is devastating and most often affects younger Veterans. There is significant long-term morbidity, a shortened life span, and a high financial burden. Because of the poor regenerative capacity of the spinal cord, development of early interventions that minimize secondary tissue injury is a priority. A major contribution to secondary tissue damage and the initiation of neuropathic pain is the inflammatory cascade triggered by activated glial cells (microglia and astroglia). This cascade begins immediately after SCI with glial release of cytokines, reactive species, and vasoactive substances. This secretome produces damage to neurons, oligodendrocytes and other cells at and beyond the level of injury through direct cytotoxic mechanisms or indirectly through the promotion of cytotoxic and vasogenic edema, vascular compromise, and tissue ischemia. These inflammatory mediators also trigger pathways that lead to chronic pain. The inflammatory cascade is further accelerated by glial production of chemokines which recruit peripheral immune cells, including neutrophils and monocytes, within the acute phase of injury. A major driver of the initial glial response is HuR, an RNA regulator that promotes expression of key inflammatory mediators through posttranscriptional mechanisms. Inflammatory mediators such as IL-1β, IL-6, TNF-α and iNOS contain adenine- and uridine-rich elements in the 3’ untranslated region (ARE) to which HuR binds and positively regulates their expression. Our prior work in SCI shows that HuR is activated in the acute phase of SCI and exacerbates injury when overexpressed in glia. Our team has developed a novel class of small molecule HuR inhibitors that blocks induction of inflammatory mediators in glial cells. In a pilot study of SCI using a mid- thoracic contusion model, we observed attenuation of clinical deficits and neuronal loss with the prototype HuR inhibitor, SRI-42127. We also found that SRI-42127 reduced allodynic pain in a peripheral nerve injury model. In this proposal we hypothesize that HuR drives expression of a pro-inflammatory and toxic secretome by resident glia that is triggered in the early stages of SCI, and that inhibiting HuR will reduce secondary tissue injury, improve motor outcome and reduce neuropathic pain. We propose 3 specific aims: (1) Further characterize the beneficial effect of HuR inhibition by SRI-42127on SCI recovery, (2) Assess mechanisms by which HuR inhibition improves recovery after SCI, and (3) Assess the contribution of glial HuR to inflammatory responses and tissue injury in SCI. The long term objectives of this proposal are to advance our small molecule HuR inhibitors as a therapy in acute SCI and to gain a mechanistic understanding of how ARE-mediated post-transcriptional regulation impacts SCI (secondary tissue injury, motor recovery and neuropathic pain). The innovation of this proposal is the investigation of a novel class of HuR inhibitors for therapeutically targeting the acute inflammatory response in SCI and the mechanistic investigation of post- transcriptional pathways (to date essentially unexplored) in SCI. The significance of this application is its focus on a treatment approach that might eventually be used in the battlefield at the time of acute injury as our preclinical studies indicate excellent and fast penetration of SRI-42127 into the central nervous system with peripheral administration, and a mitigating effect on neuronal loss and neuropathic pain. The signfiicance extends beyond SCI as the same HuR-regulated pathways drive neuroinflammation in other acute CNS injuries (e.g. traumatic brain injury or stroke) and chronic neurological diseases (e.g. ALS and Alzheimers).