Epo-dependent JAK2 Signaling in Painful Neuropathy

描述（由申请人提供）：虽然外周神经损伤后神经性疼痛状态的发病机制依赖于感觉神经轴的许多变化，但导致神经损伤部位细胞活化的初始分子事件对于保护感觉系统的结构和功能至关重要。缺氧神经局部炎性细胞因子的表达上调，并明确参与退行性神经病中神经病理性疼痛的发生和控制。促红细胞生成素（Erythropoietin，Epo）是一种受缺氧调节的造血细胞因子，可保护中枢神经系统神经元免于凋亡和缺血性死亡。我们最近报道，在慢性压迫性损伤（CCI）引起的神经病变中，Epo在周围神经损伤部位，特别是在雪旺细胞中上调。两种神经病理性疼痛动物模型的初步数据支持我们的假设，即Epo通过激活神经保护信号级联抑制疼痛行为和DRG细胞凋亡。我们提出，这些事件的机制包括逆行运输Epo共定位与其受体（EpoR）从神经损伤的DRG磷酸化JAK 2，酪氨酸激酶与EpoR，激活神经保护信号的网站。我们将通过在CCI神经病变和L5脊神经挤压损伤期间局部注射rhEpo并测量细胞凋亡和疼痛行为来测试这些假设。在体内和体外实验中，我们将预先给予干扰Epo/ EpoR功能的Epo结合拮抗剂和阻止JAK 2介导的信号传导的JAK 2药理学抑制剂。这些实验将为神经损伤和疼痛的基本机制提供新的信息，并为开发预防慢性神经病理性疼痛的新神经保护策略提供新的理论基础。

DESCRIPTION (provided by applicant): While the pathogenesis of neuropathic pain states following peripheral nerve injury is dependent on many changes in the sensory neural axis, the initial molecular events leading to the activation of cells at the site of nerve injury are critical in protecting the structure and function of sensory systems. Local expression of inflammatory cytokines is up regulated in hypoxic nerve, and are clearly implicated in the development and control of neuropathic pain in degenerating neuropathies. Erythropoietin (Epo) is a hematopoietic cytokine regulated by hypoxia in both erythroid cells and CNS neurons, which has recently been shown to protect CNS neurons from apoptosis and ischemic death. We recently reported that Epo is up regulated at the site of peripheral nerve injury, specifically in Schwann cells, during the neuropathy caused by chronic constriction injury (CCI). Preliminary data in two animal models of neuropathic pain support our hypotheses that Epo inhibits both pain behaviors and DRG apoptosis by activating neuroprotective-signaling cascades. We propose that the mechanism underlying these events includes retrograde transport of Epo colocalized with its receptor (EpoR) from the site of nerve injury to the DRG where phosphorylated JAK2, the tyrosine kinase associated with EpoR, activates neuroprotective signaling. We will test these hypotheses by injecting rhEpo locally during CCI neuropathy and L5 spinal nerve crush injury, and measuring apoptosis and pain behaviors. In both in vivo and in vitro experiments, we will preemptively administer an Epo binding antagonist that interferes with the function of Epo/ EpoR, and a pharmacological inhibitor of JAK2 that prevents JAK2- mediated signaling. The experiments will provide new information on the basic mechanisms of nerve injury and pain, and there from, new rationale for development of novel neuroprotective strategies for preventing chronic neuropathic pain.