Role of phospholipase A2 in spinal cord secondary injury

磷脂酶A2在脊髓继发性损伤中的作用 损伤后脊髓损伤有两种机制：原发性机械损伤和 由多种损伤机制介导的继发性损伤。迄今为止，三种损伤机制，即， 炎症、氧化和兴奋性神经毒性在脊髓损伤后被广泛研究 （SCI）。由于涉及多个机制，因此阻止一个特定机制不太可能 显著防止继发性SCI的进程。然而，这些不同的机制可能 可能有一个共同的中心或汇聚路径来发挥其有害影响。如果是这样， 会聚通路应导致更大的解剖和功能恢复比阻断一个单一的 通路磷脂酶是一种可以作为聚合介质的候选分子 A2（PLA2）。PLA2是一个不同的酶家族，其水解PLA2的sn-2位上的酯键。 在一个实施方案中，所述方法包括使磷脂与游离脂肪酸反应以产生游离脂肪酸如花生四烯酸（AA）和溶血磷脂。这些 产品是生物活性类花生酸和血小板活化因子（PAF）的前体， 炎症、氧化和细胞毒性的介质。此外，PLA2可以直接攻击细胞膜 诱导神经元和神经胶质细胞死亡。虽然PLA 2的下游产品，如AA，已经被广泛应用于生产。 令人惊讶的是，经过广泛的研究，我们对PLA2本身的作用和机制知之甚少， 创伤性脊髓损伤最近，我们首次证明了总PLA2和 细胞质PLA2（cPLA2; PLA2的一种亚型）的表达在急性心肌梗死后显著增加。 挫伤性SCI（Liu等人，Ann Neurol 59：606 - 619，2006）。值得注意的是，AACOCF 3，一种cPLA2抑制剂， 在SCI后30分钟给予小鼠显著减少组织损伤并改善行为 复苏在这里，我们提出了一个中心假设，即PLA2是一种会聚分子， 与继发性SCI相关的多种损伤途径。如果我们的假设是正确的 PLA2的激活应诱导多种损伤途径的抑制，因此，促进细胞的损伤。 更好的神经保护和功能恢复。因为cPLA2是最重要的 PLA2同工酶参与受体介导的AA释放，本申请将集中于PLA2同工酶的作用和 cPLA2介导SCI的作用机制。因此，提出了以下三个具体目标， 确定1）cPLA2是否作为会聚分子介导游离的细胞毒性作用， 自由基、兴奋性氨基酸和炎性细胞因子，2）cPLA2激活是否都是必需的 并足以介导继发性SCI; 3）cPLA2介导继发性SCI的机制 重点放在线粒体功能障碍上。完成此申请可能导致 开发新的有效策略，旨在促进更大的解剖和功能 SCI后的康复

Role of phospholipase A2 in spinal cord secondary injury There are two mechanisms of damage to the spinal cord after injury: a primary mechanical injury and a secondary injury mediated by multiple injury mechanisms. To date, three injury mechanisms, i.e., inflammation, oxidation and excitatory neurotoxicity, are extensively studied following spinal cord injury (SCI). Since multiple mechanisms are involved, it is unlikely that blocking one particular mechanism would significantly prevent the course of secondary SCI. However, it is possible that these different mechanisms may share a central or convergence pathway to exert their detrimental effects. If so, blocking such a convergence pathway should result in greater anatomical and functional recovery than blocking a single pathway. A candidate molecule that could serve as a convergence mediator is the enzyme phospholipase A2 (PLA2). PLA2 is a diverse family of enzymes that hydrolyze the ester bond at the sn-2 position of phospholipids to produce a free fatty acid such as arachidonic acid (AA) and a lysophospholipid. These products are precursors of bioactive eicosanoids and platelet activating factor (PAF) that are well-known mediators of inflammation, oxidation and cytotoxicity. Additionally, PLA2 can attack cell membranes directly to induce neuronal and glial death. Although the downstream products of PLA2, such as AA, have been extensively studied, to our surprise, little is known concerning the role and mechanism of the PLA2 itself in traumatic SCI. Recently, we demonstrated, for the first time, that both the activity of total PLA2 and expression of cytosolic PLA2 (cPLA2; a subtype of PLA2) increased significantly following an acute contusive SCI (Liu et al., Ann Neurol 59:606-619, 2006). Remarkably, AACOCF3, a cPLA2 inhibitor, administered at 30 min post-SCI in mice significantly reduced tissue damage and improved behavioral recovery. Here, we propose a central hypothesis that PLA2 is a convergence molecule that mediates multiple injury pathways associated with the secondary SCI. If our hypothesis is correct, blocking PLA2 activation should induce inhibition of multiple injury pathways and, therefore, promotion of greater neuroprotection and functional recovery following SCI. Since cPLA2 is the most important PLA2 isozyme implicated in receptor-mediated release of AA, this application will focus on the role and mechanisms of cPLA2 action in mediating SCI. As such, the following three specific aims are proposed to determine 1) whether cPLA2 serves as a convergence molecule mediating the cytotoxic effects of free radicals, excitatory amino acids and inflammatory cytokines, 2) whether cPLA2 activation is both necessary and sufficient to mediate secondary SCI, and 3) the mechanism by which cPLA2 mediates secondary SCI with an emphasis being placed on the mitochondria dysfunction. Completion of this application may lead to the development of novel and effective strategies aimed at promoting greater anatomical and functional recoveries after SCI.