Department of Anesthesia and Critical Care, The University of Chicago, Chicago, IL, USA.
Exp Eye Res. 2009 Nov;89(5):782-90. doi: 10.1016/j.exer.2009.07.006. Epub 2009 Jul 24.
In previous studies, inhibition of mitogen-activated protein kinase (MAP) p38 significantly improved recovery and attenuated apoptosis after retinal ischemia in rats. Yet, ischemic preconditioning (IPC) attenuated the ischemia-induced increase in p38 expression. We hypothesized that p38 was required for induction of ischemic tolerance by IPC. We examined the mechanisms of involvement of p38 in IPC neuroprotection. IPC or ischemia was induced in rat retina in vivo. Recovery after ischemia performed 24h after IPC was assessed functionally (electroretinography) and histologically at 7d after ischemia in the presence or absence of inhibition of p38. We examined the role of p38alpha in the mimicking of IPC produced by opening mitochondrial KATP channels using diazoxide, or stimulation of p38 activation by anisomycin. The importance of adenosine receptors in p38 activation after IPC was assessed using specific blockers of adenosine A1 and A2a receptors. Interfering RNA (siRNA) or SB203580 was used to block p38alpha. Phosphorylated p38 levels were measured. Phosphorylated p38 protein increased with IPC. Interfering RNA (siRNA) to p38alpha prior to IPC, or inhibiting p38 activation with SB203580, with ischemia following 24h later, significantly attenuated the neuroprotective effect of IPC. Anisomycin administered to increase p38 mimicked IPC, an effect blocked by SB203580. IPC-mimicking with diazoxide, an opener of mitochondrial KATP channels, was diminished with p38alpha siRNA. Adenosine receptor blockade did not decrease the elevated levels of phosphorylated p38 after IPC. Specific inhibition of p38alpha suggests that this MAPK is involved in the protective effects of IPC, and that p38 is downstream of mitochondrial KATP channels, but not adenosine receptors, in this neuroprotection.
在以前的研究中，抑制有丝分裂原激活的蛋白激酶（MAP）p38 显著改善了大鼠视网膜缺血后的恢复并减轻了细胞凋亡。然而，缺血预处理（IPC）减轻了缺血诱导的 p38 表达增加。我们假设 p38 是 IPC 诱导缺血耐受所必需的。我们研究了 p38 参与 IPC 神经保护的机制。在体内诱导大鼠视网膜 IPC 或缺血。在 IPC 后 24 小时进行缺血后的恢复评估，包括在存在或不存在 p38 抑制的情况下，在缺血后 7 天进行功能（视网膜电图）和组织学评估。我们研究了通过打开线粒体 KATP 通道使用二氮嗪模拟 IPC 产生时 p38 的作用，或者通过anisomycin 刺激 p38 激活。使用腺苷 A1 和 A2a 受体的特异性抑制剂评估了 IPC 后 p38 激活中腺苷受体的重要性。在 IPC 之前使用 p38alpha 的干扰 RNA（siRNA）或 SB203580 阻断 p38alpha。测量磷酸化的 p38 水平。与 IPC 相比，缺血后 24 小时后，p38alpha 的干扰 RNA（siRNA）或 SB203580 抑制 p38 激活，显著减弱了 IPC 的神经保护作用。用anisomycin 增加 p38 模拟 IPC，这种作用被 SB203580 阻断。用二氮嗪模拟 IPC，即打开线粒体 KATP 通道，用 p38alpha siRNA 减弱。腺苷受体阻断不会降低 IPC 后磷酸化 p38 的升高水平。p38alpha 的特异性抑制表明这种 MAPK 参与 IPC 的保护作用，并且 p38 是这种神经保护作用中线粒体 KATP 通道而不是腺苷受体的下游。
