Adjan V V, Hauser K F, Bakalkin G, Yakovleva T, Gharibyan A, Scheff S W, Knapp P E
Department of Anatomy and Neurobiology, 800 Rose Street, MS209, University of Kentucky, Lexington, KY 40536-0298, USA.
Neuroscience. 2007 Sep 7;148(3):724-36. doi: 10.1016/j.neuroscience.2007.05.053. Epub 2007 Aug 15.
Dynorphins are endogenous opioid peptide products of the prodynorphin gene. An extensive literature suggests that dynorphins have deleterious effects on CNS injury outcome. We thus examined whether a deficiency of dynorphin would protect against tissue damage after spinal cord injury (SCI), and if individual cell types would be specifically affected. Wild-type and prodynorphin(-/-) mice received a moderate contusion injury at 10th thoracic vertebrae (T10). Caspase-3 activity at the injury site was significantly decreased in tissue homogenates from prodynorphin(-/-) mice after 4 h. We examined frozen sections at 4 h post-injury by immunostaining for active caspase-3. At 3-4 mm rostral or caudal to the injury, >90% of all neurons, astrocytes and oligodendrocytes expressed active caspase-3 in both wild-type and knockout mice. At 6-7 mm, there were fewer caspase-3(+) oligodendrocytes and astrocytes than at 3-4 mm. Importantly, caspase-3 activation was significantly lower in prodynorphin(-/-) oligodendrocytes and astrocytes, as compared with wild-type mice. In contrast, while caspase-3 expression in neurons also declined with further distance from the injury, there was no effect of genotype. Radioimmunoassay showed that dynorphin A(1-17) was regionally increased in wild-type injured versus sham-injured tissues, although levels of the prodynorphin processing product Arg(6)-Leu-enkephalin were unchanged. Our results indicate that dynorphin peptides affect the extent of post-injury caspase-3 activation, and that glia are especially sensitive to these effects. By promoting caspase-3 activation, dynorphin peptides likely increase the probability of glial apoptosis after SCI. While normally beneficial, our findings suggest that prodynorphin or its peptide products become maladaptive following SCI and contribute to secondary injury.
强啡肽是前强啡肽基因的内源性阿片肽产物。大量文献表明，强啡肽对中枢神经系统损伤的预后有有害影响。因此，我们研究了强啡肽缺乏是否能预防脊髓损伤（SCI）后的组织损伤，以及个体细胞类型是否会受到特异性影响。野生型和前强啡肽基因敲除（-/-）小鼠在第10胸椎（T10）处接受中度挫伤。4小时后，前强啡肽基因敲除（-/-）小鼠组织匀浆中损伤部位的半胱天冬酶-3活性显著降低。我们在损伤后4小时通过免疫染色检测活性半胱天冬酶-3来检查冰冻切片。在损伤部位头侧或尾侧3-4毫米处，野生型和基因敲除小鼠中所有神经元、星形胶质细胞和少突胶质细胞的>90%都表达活性半胱天冬酶-3。在6-7毫米处，半胱天冬酶-3阳性少突胶质细胞和星形胶质细胞比在3-4毫米处少。重要的是，与野生型小鼠相比，前强啡肽基因敲除（-/-）少突胶质细胞和星形胶质细胞中的半胱天冬酶-3激活明显更低。相比之下，虽然神经元中的半胱天冬酶-3表达也随着与损伤距离的增加而下降，但基因型没有影响。放射免疫分析表明，与假手术损伤组织相比，野生型损伤组织中强啡肽A（1-17）在局部有所增加，尽管前强啡肽加工产物精氨酸（6）-亮氨酸脑啡肽的水平没有变化。我们的结果表明，强啡肽肽影响损伤后半胱天冬酶-3激活的程度，并且神经胶质细胞对这些影响特别敏感。通过促进半胱天冬酶-3激活，强啡肽肽可能增加脊髓损伤后神经胶质细胞凋亡的可能性。虽然通常是有益的，但我们的研究结果表明，前强啡肽或其肽产物在脊髓损伤后会变得适应不良并导致继发性损伤。
