Erythropoietin is a paracrine mediator of ischemic tolerance in the brain:: Evidence from an in vitro model
Erythropoietin is a paracrine mediator of ischemic tolerance in the brain:: Evidence from an in vitro model
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DOI：
10.1523/jneurosci.22-23-10291.2002
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发表时间：
2002-12-01
影响因子：
5.3
通讯作者：
Meisel, A
中科院分区：
文献类型：
--
作者：
Ruscher, K;Freyer, D;Meisel, A
在体外脑缺血模型（氧葡萄糖剥夺，OGD）中，我们研究了促红细胞生成素（EPO）是否在缺血预处理中起关键作用。我们发现，EPO的时间和剂量依赖性诱导保护大鼠原代皮层神经元对OGD。EPO应用后5 min保护作用显著，48 h达到最大值。保护作用被可溶性Epo受体（sEpoR）或抗EpoR抗体（抗EpoR）的共同应用所阻断。从OGD处理的星形胶质细胞到未处理的神经元的培养基转移诱导了神经元中对OGD的保护，这通过应用sEpoR和抗EpoR而强烈减弱。相反，从OGD处理的神经元到未处理的神经元的培养基转移诱导了不涉及EPO的针对OGD的保护。在星形胶质细胞中，OGD增强了低氧诱导因子1（HIF-1）的核转位，HIF-1是调节EPO表达的主要转录因子。因此，星形胶质细胞在OGD后EPO-mRNA的转录增加。培养的神经元表达EpoR，Janus激酶-2（JAK-2）抑制剂AG 490消除EPO诱导的对OGD的耐受。此外，EPO诱导的神经保护以及促凋亡Bcl家族成员Bad的磷酸化被磷酸肌醇-3激酶（PI 3 K）抑制剂LY 294002减少。结果表明，星形胶质细胞与OGD挑战提供旁分泌保护信号的神经元。我们提供了以下信号级联的证据：缺氧星形胶质细胞中的HIF-1被迅速激活。在HIF-1激活后，星形胶质细胞表达并释放EPO。EPO激活神经元EPO受体，随后激活JAK-2，从而激活PI 3 K。PI 3 K通过Akt介导的磷酸化使BAD失活，从而可以抑制缺氧诱导的神经元凋亡。我们的结果证实EPO是缺血预处理的重要旁分泌神经保护介质。
In an in vitro model of cerebral ischemia (oxygen glucose deprivation, OGD) we investigated whether erythropoietin (EPO) plays a critical role in ischemic preconditioning. We found that EPO time and dose-dependently induced protection against OGD in rat primary cortical neurons. Protection was significant at 5 min and reached a maximum at 48 hr after EPO application. Protection was blocked by the coapplication of a soluble Epo receptor (sEpoR) or an antibody against EpoR (anti-EpoR). Medium transfer from OGD-treated astrocytes to untreated neurons induced protection against OGD in neurons, which was attenuated strongly by the application of sEpoR and anti-EpoR. In contrast, medium transfer from OGD-treated neurons to untreated neurons induced protection against OGD that did not involve EPO. In astrocytes the OGD enhanced the nuclear translocation of hypoxia-inducible factor 1 (HIF-1), the major transcription factor regulating EPO expression. Consequently, transcription of EPO-mRNA was increased in astrocytes after OGD. Cultured neurons express EpoR, and the Janus kinase-2 (JAK-2) inhibitor AG490 abolished EPO-induced tolerance against OGD. Furthermore, EPO-induced neuroprotection as well as phosphorylation of the proapoptotic Bcl family member Bad was reduced by the phosphoinositide-3 kinase (PI3K) inhibitor LY294002. The results suggest that astrocytes challenged with OGD provide paracrine protective signals to neurons. We provide evidence for the following signaling cascade: HIF-1 is activated rapidly by hypoxia in astrocytes. After HIF-1 activation the astrocytes express and release EPO. EPO activates the neuronal EPO receptor and, subsequently, JAK-2 and thereby PI3K. PI3K deactivates BAD via Akt-mediated phosphorylation and thus may inhibit hypoxia-induced apoptosis in neurons. Our results establish EPO as an important paracrine neuroprotective mediator of ischemic preconditioning.