Mechanisms of Secondary Damage after Spinal Cord Injury

描述（由申请人提供）：脊髓损伤产生一波继发性损伤，在损伤后数小时和数天内产生持续性损伤。 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-α）的存在有关。 我们已经发现，TNF-α和红藻氨酸（KA），一种谷氨酸激动剂，联合收割机，在脊髓灰质中产生的细胞死亡比单独使用任何一种物质都多。 这种作用被AMPA/KA受体（AMPAR）拮抗剂CNQX阻断（Hermann et al，2001）。 TNF-α似乎也快速增加培养物中海马神经元表面上表达的AMPAR的数量，并增加神经元能突触后活性，这可能是通过调节组成性AMPAR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TNF-α水平都升高。 TNF增加导致细胞表面上可用的AMPAR快速增加。 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）使用共聚焦技术测定注射到运动神经元池中的TNF-α是否将增加AMPAR的细胞表面表达以测量该效应，并将该效应的时间过程与通过TNF和谷氨酸激动剂的共注射诱导的MN死亡进行比较（红藻氨酸，KA），2）我们将比较目标1的注射结果与我们已知产生类似MN细胞死亡的轻度挫伤病变，以确定损伤是否也导致细胞表面AMPAR的增加，3）我们将确定通过共注射可溶性TNFR或阻断抗体来阻断TNF-α作用是否减少了由共注射KA诱导的细胞死亡和AMPAR的表面表达增加，以及这些治疗是否可以减少轻度颈SCI后的继发性损伤。在第四个目标，我们将扩大这些研究，包括少突胶质细胞的白色物质束。 同样的策略将被用于灰质神经元。 这些研究应该提供证据来测试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SCI后继发性损伤的加重。 如果是这样的话，它可能是一个新的治疗目标。

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.