Shields D C, Schaecher K E, Hogan E L, Banik N L
Department of Neurology, Medical University of South Carolina, 171 Ashley Avenue, Charleston, SC 29425, USA.
J Neurosci Res. 2000 Jul 15;61(2):146-50. doi: 10.1002/1097-4547(20000715)61:2<146::AID-JNR5>3.0.CO;2-C.
Following traumatic injury of the spinal cord, cells adjacent to the lesion are subject to ischemic cell death as a result of vascular disruption and secondary inflammatory responses. Proteases such as calcium-activated neutral proteinase (calpain) have been implicated in axon and myelin destruction following injury since they degrade structural proteins in the axon-myelin unit. To examine the role of calpain in cell death following spinal cord injury (SCI), calpain activity and translational expression were evaluated using Western blotting techniques. Calpain activity (as measured by specific substrate degradation) was significantly increased in and around the lesion site as early as 4 hr following injury with continued elevation at 48 hr compared to sham controls. Likewise, calpain expression was significantly increased in both the lesion site and penumbra at 4 and 48 hr after injury. Using double immunofluorescent labeling for calpain and cell-specific markers, this increase in calpain expression was found to be due in part to activated glial/inflammatory cells such as astrocytes, microglia, and infiltrating macrophages in these areas. Thus, since calpain degrades many myelin and axonal structural proteins, the increased activity and expression of this enzyme may be responsible for destruction of myelinated axons adjacent to the lesion site following SCI.
脊髓遭受创伤后，由于血管破裂和继发性炎症反应，损伤部位附近的细胞会发生缺血性细胞死亡。诸如钙激活中性蛋白酶（钙蛋白酶）等蛋白酶在损伤后与轴突和髓鞘破坏有关，因为它们会降解轴突-髓鞘单元中的结构蛋白。为了研究钙蛋白酶在脊髓损伤（SCI）后细胞死亡中的作用，使用蛋白质印迹技术评估了钙蛋白酶活性和翻译表达。与假手术对照组相比，损伤后4小时，损伤部位及其周围的钙蛋白酶活性（通过特定底物降解来测量）就显著增加，48小时时持续升高。同样，损伤后4小时和48小时，损伤部位和半暗带中的钙蛋白酶表达均显著增加。使用针对钙蛋白酶和细胞特异性标志物的双重免疫荧光标记，发现这些区域中钙蛋白酶表达的增加部分归因于活化的神经胶质/炎症细胞，如星形胶质细胞、小胶质细胞和浸润的巨噬细胞。因此，由于钙蛋白酶会降解许多髓鞘和轴突结构蛋白，该酶活性和表达的增加可能是SCI后损伤部位附近有髓轴突破坏的原因。
