Koponen S, Keinänen R, Roivainen R, Hirvonen T, Närhi M, Chan P H, Koistinaho J
A.I. Virtanen Institute, University of Kuopio, Finland.
Neuroscience. 1999;93(3):985-93. doi: 10.1016/s0306-4522(99)00166-9.
Spreading depression is a wave of sustained depolarization challenging the energy metabolism of the cells without causing irreversible damage. In the ischaemic brain, sreading depression-like depolarization contributes to the evolution of ischaemia to infarction. The depolarization is propagated by activation of N-methyl-D-aspartate receptors, but changes in signal transduction downstream of the receptors are not known. Because protein phosphorylation is a general mechanism whereby most cellular processes are regulated, and inhibition of N-methyl-D-aspartate receptors or protein kinase C is neuroprotective, the expression of protein kinase C subspecies in spreading depression was examined. Cortical treatment with KCl induced an upregulation of protein kinase Cdelta and zeta messenger RNA at 4 and 8 h, whereas protein kinase Calpha, beta, gamma and epsilon did not show significant changes. The gene induction was the strongest in layers 2 and 3, and was followed by an increased number of protein kinase Cdelta-immunoreactive neurons. Protein kinase Cdelta and zeta inductions were inhibited by pretreatment with an N-methyl-D-aspartate receptor antagonist, dizocilpine maleate, which also blocked spreading depression propagation, and with dexamethasone, which acted without blocking the propagation. Quinacrine, a phospholipase A2 inhibitor, reduced only protein kinase C5 induction. In addition, N(G)(-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, did not influence protein kinase Cdelta or zeta induction, whereas 6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione, an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate/kainate receptor antagonist, and the cyclo-oxygenase inhibitors indomethacin and diclophenac tended to increase gene expression. The data show that cortical spreading depression induces Ca2(+)-independent protein kinase C subspecies delta and zeta, but not Ca(2+)-dependent subspecies, through activation of N-methyl-D-aspartate receptors and phospholipase A2. Even though the signal pathway is similar to the induction described previously in ischaemia for genes implicated in delayed neuronal death, the gene inductions observed here are not necessarily pathogenetic, but may represent a general reaction to metabolic stress.
扩散性抑制是一种持续去极化波，它对细胞的能量代谢构成挑战，但不会造成不可逆损伤。在缺血性脑损伤中，类似扩散性抑制的去极化会促使缺血发展为梗死。这种去极化是通过N-甲基-D-天冬氨酸受体的激活来传播的，但受体下游信号转导的变化尚不清楚。由于蛋白质磷酸化是调节大多数细胞过程的普遍机制，并且抑制N-甲基-D-天冬氨酸受体或蛋白激酶C具有神经保护作用，因此研究了扩散性抑制中蛋白激酶C亚型的表达。用氯化钾处理皮层会在4小时和8小时时诱导蛋白激酶Cδ和ζ信使核糖核酸上调，而蛋白激酶Cα、β、γ和ε则未显示出显著变化。这种基因诱导在第2层和第3层中最强，随后蛋白激酶Cδ免疫反应性神经元数量增加。用N-甲基-D-天冬氨酸受体拮抗剂马来酸氯氮平预处理可抑制蛋白激酶Cδ和ζ的诱导，马来酸氯氮平还能阻断扩散性抑制的传播，用地塞米松预处理也可抑制，地塞米松在不阻断传播的情况下发挥作用。喹那克林是一种磷脂酶A2抑制剂，仅能降低蛋白激酶Cδ的诱导。此外，一氧化氮合酶抑制剂N(G)-硝基-L-精氨酸甲酯不影响蛋白激酶Cδ或ζ的诱导，而α-氨基-3-羟基-5-甲基-4-异恶唑丙酸/海人藻酸受体拮抗剂6-硝基-7-氨磺酰基苯并[f]喹喔啉-2,3-二酮以及环氧化酶抑制剂吲哚美辛和双氯芬酸则倾向于增加基因表达。数据表明，皮层扩散性抑制通过激活N-甲基-D-天冬氨酸受体和磷脂酶A2诱导不依赖Ca2+的蛋白激酶C亚型δ和ζ，而非依赖Ca2+的亚型。尽管该信号通路与先前在缺血中描述的与延迟性神经元死亡相关基因的诱导相似，但此处观察到的基因诱导不一定是致病的，而可能代表对代谢应激的一种普遍反应。
