Integrated Omics Center, Life/Health Division, Korea Institute of Science and Technology (KIST), P.O. Box 131, Cheongryang, Seoul 130-650, Korea.
Arch Pharm Res. 2011 Jun;34(6):1023-34. doi: 10.1007/s12272-011-0620-3. Epub 2011 Jul 2.
Ischemic preconditioning can provide protection to neurons from subsequent lethal ischemia. The molecular mechanisms of neuronal ischemic tolerance, however, are still not well-known. The present study, therefore, examined the role of MAPK and PI3K/Akt pathways in ischemic tolerance induced by preconditioning with sublethal oxygen-glucose deprivation (OGD) in cultured rat cortical neurons. Ischemic tolerance was simulated by preconditioning of the neurons with sublethal 1-h OGD imposed 12 h before lethal 3-h OGD. The time-course studies of relative phosphorylation and expression levels of ERK1/2, JNK and p38 MAPK showed lack of their involvement in ischemic tolerance. However, there were significant increases in Akt phosphorylation levels during the reperfusion period following preconditioned lethal OGD. In addition, Bcl-2 associated death promoter (Bad) and GSK-3β were also found to be inactivated during that reperfusion period. Finally, treatment with an inhibitor of PI3K, wortmannin, applied from 15 min before and during lethal OGD abolished not only the preconditioning-induced neuroprotection but also the Akt activation. Concomitant with blockade of the Akt activation, PI3K inhibition also resulted in activation of Bad and GSK-3β. The results suggest that ischemic tolerance induced by sublethal OGD preconditioning is primarily mediated through activation of the PI3K/Akt pathway, but not the MAPK pathway, in rat cortical neurons.
缺血预处理可以为神经元提供后续致命性缺血的保护。然而，神经元缺血耐受的分子机制尚不清楚。因此，本研究检测了 MAPK 和 PI3K/Akt 通路在亚致死性氧葡萄糖剥夺（OGD）预处理诱导的培养大鼠皮质神经元缺血耐受中的作用。通过在 3 小时致命性 OGD 之前 12 小时对神经元进行亚致死性 1 小时 OGD 预处理来模拟缺血耐受。ERK1/2、JNK 和 p38 MAPK 的相对磷酸化和表达水平的时程研究表明它们不参与缺血耐受。然而，在预处理致死性 OGD 后的再灌注期间，Akt 磷酸化水平显著增加。此外，在再灌注期间还发现 Bcl-2 相关死亡促进剂（Bad）和 GSK-3β失活。最后，在致死性 OGD 之前 15 分钟和期间应用 PI3K 抑制剂wortmannin，不仅消除了预处理诱导的神经保护作用，还消除了 Akt 的激活。伴随着 Akt 激活的阻断，PI3K 抑制也导致 Bad 和 GSK-3β的激活。结果表明，亚致死性 OGD 预处理诱导的缺血耐受主要通过激活大鼠皮质神经元中的 PI3K/Akt 通路，而不是 MAPK 通路来介导。
