Smith Ian F, Boyle John P, Green Kim N, Pearson Hugh A, Peers Chris
Institute for Cardiovascular Research School of Biomedical Sciences, University of Leeds, Leeds, UK.
J Neurochem. 2004 Feb;88(4):869-77. doi: 10.1046/j.1471-4159.2003.02212.x.
Chronic hypoxia (CH) alters Ca2+ homeostasis in various cells and may contribute to disturbed Ca2+ homeostasis of Alzheimer's disease. Here, we have employed microfluorimetric measurements of [Ca2+]i to investigate the mechanism underlying augmentation of Ca2+ signalling by chronic hypoxia in type I cortical astrocytes. Application of bradykinin evoked significantly larger rises of [Ca2+]i in hypoxic cells as compared with control cells. This augmentation was prevented fully by either melatonin (150 micro m) or ascorbic acid (200 micro m), indicating the involvement of reactive oxygen species. Given the association between hypoxia and increased production of amyloid beta peptides (AbetaPs) of Alzheimer's disease, we performed immunofluorescence studies to show that hypoxia caused a marked and consistent increased staining for AbetaPs and presenilin-1 (PS-1). Western blot experiments also confirmed that hypoxia increased PS-1 protein levels. Hypoxic increases of AbetaP production was prevented with inhibitors of either gamma- or beta-secretase. These inhibitors also partially prevented the augmentation of Ca2+ signalling in astrocytes. Our results indicate that chronic hypoxia enhances agonist-evoked rises of [Ca2+]i in cortical astrocytes, and that this can be prevented by antioxidants and appears to be associated with increased AbetaP formation.
慢性缺氧（CH）会改变多种细胞内的钙离子稳态，可能导致阿尔茨海默病患者钙离子稳态紊乱。在此，我们采用微荧光法测量细胞内钙离子浓度（[Ca2+]i），以研究I型皮质星形胶质细胞中慢性缺氧增强钙离子信号传导的机制。与对照细胞相比，应用缓激肽后，缺氧细胞内[Ca2+]i的升高幅度明显更大。褪黑素（150 μmol）或抗坏血酸（200 μmol）可完全阻止这种增强作用，表明活性氧参与其中。鉴于缺氧与阿尔茨海默病患者淀粉样β肽（AβP）生成增加之间的关联，我们进行了免疫荧光研究，结果显示缺氧导致AβP和早老素-1（PS-1）的染色显著且持续增加。蛋白质印迹实验也证实缺氧会增加PS-1蛋白水平。γ-或β-分泌酶抑制剂可阻止缺氧引起的AβP生成增加。这些抑制剂还可部分阻止星形胶质细胞中钙离子信号传导的增强。我们的结果表明，慢性缺氧会增强皮质星形胶质细胞中激动剂诱发的[Ca2+]i升高，而抗氧化剂可阻止这种升高，且这似乎与AβP生成增加有关。
