Büki A, Siman R, Trojanowski J Q, Povlishock J T
Department of Anatomy, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298-0709, USA.
J Neuropathol Exp Neurol. 1999 Apr;58(4):365-75. doi: 10.1097/00005072-199904000-00007.
In animals and man, traumatic brain injury (TBI) results in axonal injury (AI) that contributes to morbidity and mortality. Such injured axons show progressive change leading to axonal disconnection. Although several theories implicate calcium in the pathogenesis of AI, experimental studies have failed to confirm its pivotal role. To explore the contribution of Ca2+-induced proteolysis to axonal injury, this study was undertaken in an animal model of TBI employing antibodies targeting both calpain-mediated spectrin proteolysis (CMSP) and focal neurofilament compaction (NFC), a marker of intra-axonal cytoskeletal perturbation, at 15-120 minutes (min) postinjury. Light microscopy (LM) revealed that TBI consistently evoked focal, intra-axonal CMSP that was spatially and temporally correlated with NFC. These changes were seen at 15 min postinjury with significantly increasing number of axons demonstrating CMSP immunoreactivity over time postinjury. Electron microscopy (EM) demonstrated that at 15 min postinjury CMSP was confined primarily to the subaxolemmal network. With increasing survival (30-120 min) CMSP filled the axoplasm proper. These findings provide the first direct evidence for focal CMSP in the pathogenesis of generalized/diffuse AI. Importantly, they also reveal an initial subaxolemmal involvement prior to induction of a more widespread axoplasmic change indicating a spatial-temporal compartmentalization of the calcium-induced proteolytic process that may be amenable to rapid therapeutic intervention.
在动物和人类中，创伤性脑损伤（TBI）会导致轴突损伤（AI），这会增加发病率和死亡率。这种受损的轴突会出现渐进性变化，导致轴突断开连接。尽管有几种理论认为钙在轴突损伤的发病机制中起作用，但实验研究未能证实其关键作用。为了探究Ca2+诱导的蛋白水解对轴突损伤的作用，本研究在TBI动物模型中进行，在损伤后15 - 120分钟使用针对钙蛋白酶介导的血影蛋白水解（CMSP）和局灶性神经丝致密化（NFC，轴突内细胞骨架扰动的标志物）的抗体。光学显微镜（LM）显示，TBI始终会诱发局灶性的轴突内CMSP，其在空间和时间上与NFC相关。这些变化在损伤后15分钟即可见到，随着损伤后时间的推移，显示CMSP免疫反应性的轴突数量显著增加。电子显微镜（EM）表明，损伤后15分钟时，CMSP主要局限于轴突下膜网络。随着存活时间增加（30 - 120分钟），CMSP充满了轴突浆。这些发现为全身性/弥漫性AI发病机制中的局灶性CMSP提供了首个直接证据。重要的是，它们还揭示了在诱导更广泛的轴突浆变化之前，轴突下膜最初就已受累，这表明钙诱导的蛋白水解过程存在时空分隔，这可能适合快速的治疗干预。
