Mechanisms of Secondary Damage after Spinal Cord Injury

描述(由申请人提供)：脊髓损伤会产生一波继发性损伤，在侮辱后的几个小时和几天内产生持续的损伤。继发性损伤的早期似乎与兴奋性毒性细胞死亡和炎性细胞因子的存在有关，如肿瘤坏死因子-α(TNF-a)。我们已经发现，肿瘤坏死因子-a和谷氨酸激动剂海人酸(KA)结合在一起，在脊髓灰质中产生的细胞死亡比单独使用这两种物质要多得多。这一作用可被AMPA/KA受体(AMPAR)拮抗剂CNQX阻断(Hermann等，2001)。肿瘤坏死因子-α似乎还能迅速增加培养的海马神经元表面表达的AMPAR的数量，并增加谷氨酸能突触后活性，这可能是通过调节结构性AMPAR的运输(E.Beattie等人，2002)。我们的假设是，在脊髓挫伤后的几分钟内，谷氨酸和肿瘤坏死因子-a的水平都会上升。肿瘤坏死因子的增加导致细胞表面可利用的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敏感性。我们提出了以下具体目标：1)利用共聚焦技术来测量这种影响，并将这种影响的时间进程与联合注射肿瘤坏死因子和谷氨酸激动剂(海人酸，KA)诱导的MN死亡进行比较，以确定向运动神经元池中注射肿瘤坏死因子-α是否会增加AMPAR的细胞表面表达；2)我们将比较AIM 1和我们知道会产生类似MN细胞死亡的轻度挫伤损伤的结果，以确定损伤是否也会导致细胞表面AMPAR的增加，3)我们将确定通过联合注射可溶性肿瘤坏死因子受体或阻断抗体来阻断肿瘤坏死因子-α的作用是否可以减少联合注射KA引起的细胞死亡和AMPAR表面表达的增加，以及这些治疗是否可以减少轻度颈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以包括白质束的少突胶质细胞。同样的策略也将用于灰质神经元。这些研究应该提供证据来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。如果是这样的话，它可能成为治疗的新靶点。

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.