Hayashi Takeshi, Saito Atsushi, Okuno Shuzo, Ferrand-Drake Michel, Chan Pak H
Department of Neurosurgery, Department of Neurology and Neurological Sciences, and Program in Neurosciences, Stanford University School of Medicine, Stanford, California 94305, U.S.A.
J Cereb Blood Flow Metab. 2003 Aug;23(8):949-61. doi: 10.1097/01.WCB.0000077641.41248.EA.
Although the endoplasmic reticulum (ER) is implicated in neuronal degeneration in some situations, its role in delayed neuronal cell death (DND) after ischemia remains uncertain. The authors speculated that ER stress is involved in DND, that it is reduced by ischemic preconditioning, and that ER stress reduction by preconditioning is due to ER molecular chaperone induction. The phosphorylation status of eukaryotic initiation factor 2alpha (eIF2alpha) and RNA-dependent protein kinase-like ER eIF2alpha kinase (PERK) was investigated in the rat hippocampus after ischemia with and without preconditioning. PERK is phosphorylated by ER stress, which phosphorylates eIF2alpha. To investigate the role of ER molecular chaperones in preconditioning, the authors examined GRP78 and GRP94 expression, both of which are ER chaperones that inhibit PERK phosphorylation, and compared their induction and ischemic tolerance time windows. Phosphorylation of eIF2alpha and PERK was confirmed after severe ischemia but was inhibited by preconditioning. After preconditioning, GRP78 was increased in the brain with a peak at 2 days, which corresponded with the ischemic tolerance time window. Immunoprecipitation and double staining demonstrated involvement of GRP78 in prevention of PERK phosphorylation. These results suggest that GRP78 induced by preconditioning may reduce ER stress and eventual DND after ischemia.
尽管在内质网（ER）在某些情况下与神经元变性有关，但其在缺血后延迟性神经元细胞死亡（DND）中的作用仍不确定。作者推测内质网应激参与了延迟性神经元细胞死亡，缺血预处理可减轻内质网应激，且预处理减轻内质网应激是由于诱导了内质网分子伴侣。研究了在有或无预处理的情况下，大鼠缺血后海马体中真核起始因子2α（eIF2α）和RNA依赖性蛋白激酶样内质网eIF2α激酶（PERK）的磷酸化状态。PERK在内质网应激时被磷酸化，进而使eIF2α磷酸化。为了研究内质网分子伴侣在预处理中的作用，作者检测了GRP78和GRP94的表达，这两种都是抑制PERK磷酸化的内质网伴侣蛋白，并比较了它们的诱导情况和缺血耐受时间窗。严重缺血后证实了eIF2α和PERK的磷酸化，但预处理可抑制其磷酸化。预处理后，大脑中GRP78增加，在第2天达到峰值，这与缺血耐受时间窗相对应。免疫沉淀和双重染色表明GRP78参与了预防PERK磷酸化。这些结果表明，预处理诱导的GRP78可能减轻缺血后的内质网应激和最终的延迟性神经元细胞死亡。
