Sieber F E, Traystman R J, Martin L J
Department of Anesthesiology, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA.
J Cereb Blood Flow Metab. 1997 May;17(5):527-33. doi: 10.1097/00004647-199705000-00006.
Activation of phospholipase C (PLC) increases intracellular Ca2+ and may play a role in delayed neuronal death after ischemia. Because changes in intracellular Ca2+ are believed to participate in ischemic neuronal injury, we tested the hypothesis that PLC beta protein levels are temporally altered in brain regions that undergo neurodegeneration after global incomplete ischemia. Dogs (n = 12) were subjected to 20 minutes of global incomplete ischemia followed by recovery of either 1 (n = 5) or 7 days (n = 7). Six sham-operated animals were used as nonischemic controls. In hematoxylin and eosin-stained brain sections, neuronal density at 1 day after ischemia was unchanged relative to nonischemic controls in hippocampus CA1, caudate, and cerebellar cortex (anterior lobule). However, at 7 days after ischemia, neuronal densities were decreased to 56 +/- 15% (mean +/- SD) and 75 +/- 17% of control in CA1 and caudate, respectively. At 1 and 7 days after ischemia, the percentage of neurons showing ischemic injury increased from 13 +/- 10 to 40 +/- 35% in CA1, 24 +/- 25 to 59 +/- 16% in cerebellum, and 4 +/- 2 to 18 +/- 12% in caudate. Densitometric analysis of immunocytochemically stained brain sections from controls (n = 3). 1 day after ischemia (n = 3), and 7 days after ischemia (n = 5) revealed that PLC beta immunoreactivity was increased in cerebellum at 1 day (0.274 +/- 0.013 v 0.295 +/- 0.005 optical density units [OD] in control and 1 day, respectively) and 7 days (0.108 +/- 0.009 v 0.116 +/- 0.005 O.D. in control and 7 days, respectively). PLC beta immunoreactivity was unchanged after ischemia in caudate and hippocampus. Western blot analysis of PLC beta immunoreactivity in the cerebellar cortex and hippocampus in the control (n = 3), 1 day (n = 2), and 7 days after ischemia (n = 2) groups showed that PLC beta levels were increased after ischemia in cerebellum 266% and 227% above control at 1 and 7 days, respectively. However, in hippocampus, PLC expression after ischemia was unchanged at 97% and 84% of control at 1 and 7 days, respectively. These results show that delayed neuronal degeneration after global incomplete ischemia is accompanied by regional abnormalities in PLC levels. Elevated PLC levels early may represent an aberrant signal transduction mechanism resulting in delayed cell damage, whereas decreased PLC levels later after ischemia may reflect ongoing neurodegeneration.
磷脂酶C（PLC）的激活会增加细胞内钙离子浓度，可能在缺血后延迟性神经元死亡中发挥作用。由于细胞内钙离子浓度的变化被认为参与了缺血性神经元损伤，我们检验了以下假设：在全脑不完全缺血后发生神经退行性变的脑区，PLCβ蛋白水平会随时间发生改变。将12只犬进行20分钟的全脑不完全缺血，随后分别恢复1天（n = 5）或7天（n = 7）。6只假手术动物作为非缺血对照。在苏木精-伊红染色的脑切片中，缺血1天后海马CA1区、尾状核和小脑皮质（前叶）的神经元密度相对于非缺血对照无变化。然而，缺血7天后，CA1区和尾状核的神经元密度分别降至对照的56±15%（平均值±标准差）和75±17%。缺血1天和7天后，显示缺血损伤的神经元百分比在CA1区从13±10%增加到40±35%，在小脑从24±25%增加到59±16%，在尾状核从4±2%增加到18±12%。对来自对照组（n = 3）、缺血1天（n = 3）和缺血7天（n = 5）的免疫细胞化学染色脑切片进行光密度分析，结果显示，缺血1天（对照组和1天组的光密度单位[OD]分别为0.274±0.013和0.295±0.005）和7天（对照组和7天组的OD分别为0.108±0.009和0.116±0.005）时，小脑中PLCβ免疫反应性增加。缺血后尾状核和海马中的PLCβ免疫反应性无变化。对对照组（n = 3）、缺血1天（n = 2）和缺血7天（n = 2）组的小脑皮质和海马中的PLCβ免疫反应性进行蛋白质印迹分析，结果显示，缺血后小脑在1天和7天时PLCβ水平分别比对照升高266%和227%。然而，在海马中，缺血后1天和7天时PLC表达分别为对照的97%和84%，无变化。这些结果表明，全脑不完全缺血后延迟性神经元变性伴随着PLC水平的区域异常。早期PLC水平升高可能代表一种异常的信号转导机制，导致延迟性细胞损伤，而缺血后期PLC水平降低可能反映正在进行的神经退行性变。
