Gonzalez-Zulueta M, Feldman A B, Klesse L J, Kalb R G, Dillman J F, Parada L F, Dawson T M, Dawson V L
Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
Proc Natl Acad Sci U S A. 2000 Jan 4;97(1):436-41. doi: 10.1073/pnas.97.1.436.
The mechanisms underlying neuronal ischemic preconditioning, a phenomenon in which brief episodes of ischemia protect against the lethal effects of subsequent periods of prolonged ischemia, are poorly understood. Ischemia can be modeled in vitro by oxygen-glucose deprivation (OGD). We report here that OGD preconditioning induces p21(ras) (Ras) activation in an N-methyl-D-aspartate receptor- and NO-dependent, but cGMP-independent, manner. We demonstrate that Ras activity is necessary and sufficient for OGD tolerance in neurons. Pharmacological inhibition of Ras, as well as a dominant negative mutant Ras, block OGD preconditioning whereas a constitutively active form of Ras promotes neuroprotection against lethal OGD insults. In contrast, the activity of phosphatidyl inositol 3-kinase is not required for OGD preconditioning because inhibition of phosphatidyl inositol 3-kinase with a chemical inhibitor or with a dominant negative mutant does not have any effect on the development of OGD tolerance. Furthermore, using recombinant adenoviruses and pharmacological inhibitors, we show that downstream of Ras the extracellular regulated kinase cascade is required for OGD preconditioning. Our observations indicate that activation of the Ras/extracellular regulated kinase cascade by NO is a critical mechanism for the development of OGD tolerance in cortical neurons, which may also play an important role in ischemic preconditioning in vivo.
神经元缺血预处理是一种短暂的缺血发作可保护机体免受随后长时间缺血致死效应的现象，但其潜在机制仍知之甚少。缺血可通过体外氧糖剥夺（OGD）来模拟。我们在此报告，OGD预处理以一种依赖N-甲基-D-天冬氨酸受体和NO但不依赖cGMP的方式诱导p21(ras)（Ras）激活。我们证明Ras活性对于神经元的OGD耐受性是必要且充分的。对Ras的药理学抑制以及显性负性突变体Ras均可阻断OGD预处理，而组成型活性形式的Ras则促进对致死性OGD损伤的神经保护作用。相比之下，磷脂酰肌醇3激酶的活性对于OGD预处理并非必需，因为用化学抑制剂或显性负性突变体抑制磷脂酰肌醇3激酶对OGD耐受性的形成没有任何影响。此外，使用重组腺病毒和药理学抑制剂，我们表明在Ras的下游，细胞外调节激酶级联反应对于OGD预处理是必需的。我们的观察结果表明，NO介导的Ras/细胞外调节激酶级联反应的激活是皮质神经元OGD耐受性形成的关键机制，这在体内缺血预处理中可能也起重要作用。
