Costain Willard J, Rasquinha Ingrid, Sandhu Jagdeep K, Rippstein Peter, Zurakowski Bogdan, Slinn Jacqueline, MacManus John P, Stanimirovic Danica B
Glycosyltransferase and Neuroglycomics, Institute for Biological Sciences, National Research Council, Ottawa, Ontario, Canada.
J Cereb Blood Flow Metab. 2008 Jan;28(1):99-110. doi: 10.1038/sj.jcbfm.9600510. Epub 2007 May 16.
Synaptic pathology is observed during hypoxic events in the central nervous system in the form of altered dendrite structure and conductance changes. These alterations are rapidly reversible, on the return of normoxia, but are thought to initiate subsequent neuronal cell death. To characterize the effects of hypoxia on regulators of synaptic stability, we examined the temporal expression of cell adhesion molecules (CAMs) in synaptosomes after transient middle cerebral artery occlusion (MCAO) in mice. We focused on events preceding the onset of ischemic neuronal cell death (<48 h). Synaptosome preparations were enriched in synaptically localized proteins and were free of endoplasmic reticulum and nuclear contamination. Electron microscopy showed that the synaptosome preparation was enriched in spheres (approximately 650 nm in diameter) containing secretory vesicles and postsynaptic densities. Forebrain mRNA levels of synaptically located CAMs was unaffected at 3 h after MCAO. This is contrasted by the observation of consistent downregulation of synaptic CAMs at 20 h after MCAO. Examination of synaptosomal CAM protein content indicated that certain adhesion molecules were decreased as early as 3 h after MCAO. For comparison, synaptosomal Agrn protein levels were unaffected by cerebral ischemia. Furthermore, a marked increase in the levels of p-Ctnnb1 in ischemic synaptosomes was observed. p-Ctnnb1 was detected in hippocampal fiber tracts and in cornu ammonis 1 neuronal nuclei. These results indicate that ischemia induces a dysregulation of a subset of synaptic proteins that are important regulators of synaptic plasticity before the onset of ischemic neuronal cell death.
在中枢神经系统的缺氧事件中，可观察到突触病理学变化，表现为树突结构改变和电导变化。这些改变在恢复常氧后可迅速逆转，但被认为会引发随后的神经元细胞死亡。为了表征缺氧对突触稳定性调节因子的影响，我们检测了小鼠短暂大脑中动脉闭塞（MCAO）后突触体中细胞粘附分子（CAMs）的时间表达。我们关注缺血性神经元细胞死亡开始前（<48小时）的事件。突触体制备物富含突触定位蛋白，且无内质网和核污染。电子显微镜显示，突触体制备物富含含有分泌囊泡和突触后致密物的球体（直径约650nm）。MCAO后3小时，突触定位的CAMs的前脑mRNA水平未受影响。与此形成对比的是，在MCAO后20小时观察到突触CAMs持续下调。对突触体CAM蛋白含量的检测表明，某些粘附分子在MCAO后3小时就开始减少。作为对照，突触体Agrn蛋白水平不受脑缺血影响。此外，在缺血性突触体中观察到p-Ctnnb1水平显著升高。在海马纤维束和海马1区神经元核中检测到p-Ctnnb1。这些结果表明，缺血在缺血性神经元细胞死亡开始前会诱导一部分突触蛋白失调，而这些蛋白是突触可塑性的重要调节因子。
