Mechanisms of Secondary Damage after Spinal Cord Injury

描述（由申请人提供）：脊髓损伤产生继发性损伤波，在损伤后数小时或数天内产生持续损伤。继发性损伤的早期阶段似乎与兴奋性毒性细胞死亡和炎性细胞因子如肿瘤坏死因子- α (TNF-a)的存在有关。我们发现，TNF-a和谷氨酸激动剂kainic酸（KA）结合在一起，比单独使用任何一种物质，在脊髓灰质中产生更多的细胞死亡。这种作用被AMPA/KA受体（AMPAR）拮抗剂CNQX阻断（Hermann et al, 2001）。TNF-a似乎还能迅速增加培养海马神经元表面表达的AMPAR数量，并增加谷氨酸突触后活性，这可能是通过调节构成性AMPAR运输（E. Beattie et al, 2002）。我们的假设是，在脊髓挫伤后的几分钟内，谷氨酸和TNF-a水平都上升了。TNF的增加导致细胞表面可用的ampar迅速增加。这增加了脊髓神经元对谷氨酸诱导的细胞死亡的易感性。我们提出以下具体目标：1)确定注入运动神经元池的TNF-a是否会增加AMPARs的细胞表面表达，使用共聚焦技术测量这种效应，并将这种效应的时间过程与联合注射TNF和谷氨酸激动剂（kainic acid， KA）诱导的MN死亡进行比较；2)我们将比较aim 1的注射结果与我们所知道的产生相似MN细胞死亡的轻度挫伤病变的结果，以确定损伤是否也导致细胞表面AMPARs的增加。3)我们将确定通过联合注射可溶性TNFR或阻断抗体来阻断TNF-a的作用是否可以减少联合注射KA引起的细胞死亡和AMPARs表面表达的增加，以及这些治疗是否可以减少轻度颈椎脊髓损伤后的继发性损伤。在第四个目标中，我们将扩展这些研究，包括白质束的少突胶质细胞。同样的策略将用于灰质神经元。这些研究应该为检验细胞因子和神经递质之间的这种新的相互作用是否可能参与脊髓损伤后继发性损伤的加重提供证据。如果是这样，它可能成为治疗的新目标。

DESCRIPTION (provided by applicant): Spinal cord damage produces a wave of secondary injury that produces continuing damage over the hours and days following insult. It appears that an early phase of secondary injury is related to excitotoxic cell death and the presence of inflammatory cytokines like tumor necrosis factor-alpha (TNF-a). We have found that TNF-a and kainic acid (KA), a glutamate agonist, combine to produce much more cell death in the spinal gray matter than either substance alone. This effect is blocked by an AMPA/KA receptor (AMPAR) antagonist, CNQX (Hermann et al, 2001). TNF-a also appears to rapidly increase the number of AMPARs expressed on the surface of hippocampal neurons in culture, and increases glutamatergic post-synaptic activity, probably through modulation of constitutive AMPAR trafficking (E. Beattie et al, 2002). Our hypothesis is that in the minutes following spinal cord contusion, both glutamate and TNF-a levels rise. The TNF increase results in the rapid increase in AMPARs available on the cell surface. This increases the susceptibility of spinal neurons to glutamate-induced cell death. We propose the following specific aims: 1) Determine whether TNF-a injected into motoneuron pools will increase the cell surface expression of AMPARs using confocal techniques for measuring this effect and compare the time course of this effect with this with MN death induced by co-injections of TNF and glutamate agonists (kainic acid, KA), 2) We will compare the results of injections from aim 1 to mild contusion lesions that we know produce similar MN cell death to determine if injury also results in increases in cell surface AMPARs, 3) We will determine whether blockade of TNF-a action by co-injection of soluble TNFR or blocking antibodies reduces both cell death induced by co-injection of KA and increased surface expression of AMPARs, and whether these treatments can reduce secondary injury after mild cervical SCI. In the fourth aim, we will extend these studies to include oligodendrocytes of the white matter tracts. The same strategies will be used as for gray matter neurons. These studies should provide evidence to test whether this novel interaction between a cytokine and a neurotransmitter may be involved in the exacerbation of secondary injury following SCI. If so, it may be a new target for therapies.