Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310009, China.
Neurochem Int. 2011 Apr;58(5):549-57. doi: 10.1016/j.neuint.2011.01.013. Epub 2011 Jan 15.
Dexmedetomidine (DEX) has been found to improve neuronal survival after transient global or focal cerebral ischemia in rats. Astrocyte cells may possess beneficial properties that promote neuronal recovery by secreting neurotrophic factors, such as glial cell line-derived neurotrophic factor (GDNF). The purpose of this study was to investigate the effects of DEX on GDNF release from astrocytes and the possible mechanisms involved. Astrocyte cells were treated with DEX, and GDNF level in the conditioned media was determined by ELISA assay. The expression of CREB, p-CREB and PKCα was analyzed by Western blotting to explore the mechanisms involved in GDNF release. Our results showed that DEX stimulated GDNF release in a time- and dose-dependent manner; and this stimulation was blocked by the α2-adrenoreceptor antagonist yohimbine, but not by α1-adrenoreceptor antagonist prasozin, demonstrating that DEX induced GDNF release likely acts via activating the α2A adrenoreceptor. In addition, DEX-stimulated GDNF release was also blocked by the universal PKC inhibitor Ro-318220 and PKCα/β inhibitor Gö 6976, but not by PKCδ inhibitor rottlerin and PKCβ inhibitor LY333531. Interestingly, DEX also activated CREB phosphorylation, which was inhibited by Ro-318220, Gö 697 and ERK kinase inhibitor PD98059. Silencing CREB by siRNA decreased the DEX-stimulated GDNF release. In addition, the membrane translocation of PKCα was enhanced following DEX treatment. Furthermore, we found that DEX stimulated GDNF release rescued neurons against OGD-induced neurotoxicity; this effect was partly abolished by GDNF antibody. Thus, through α2A adrenergic receptors, DEX may activate astrocytes, and promote GDNF release to protect neurons after stroke, and this signaling is possibly dependent on PKCα and CREB activation.
右美托咪定（DEX）已被发现可改善大鼠短暂性全脑或局灶性脑缺血后的神经元存活。星形胶质细胞可能具有通过分泌神经营养因子（如胶质细胞系源性神经营养因子（GDNF））促进神经元恢复的有益特性。本研究旨在探讨 DEX 对星形胶质细胞中 GDNF 释放的影响及其可能涉及的机制。用 DEX 处理星形胶质细胞，通过 ELISA 测定条件培养基中 GDNF 的水平。通过 Western 印迹分析 CREB、p-CREB 和 PKCα 的表达，以探讨 GDNF 释放涉及的机制。我们的结果表明，DEX 以时间和剂量依赖的方式刺激 GDNF 释放；这种刺激被α2-肾上腺素受体拮抗剂育亨宾阻断，但被α1-肾上腺素受体拮抗剂哌唑嗪阻断，表明 DEX 诱导 GDNF 释放可能通过激活α2A 肾上腺素受体起作用。此外，DEX 刺激的 GDNF 释放也被普遍的 PKC 抑制剂 Ro-318220 和 PKCα/β抑制剂 Gö 6976 阻断，但不被 PKCδ抑制剂 rottlerin 和 PKCβ抑制剂 LY333531 阻断。有趣的是，DEX 还激活了 CREB 磷酸化，该磷酸化被 Ro-318220、Gö 697 和 ERK 激酶抑制剂 PD98059 抑制。用 siRNA 沉默 CREB 可减少 DEX 刺激的 GDNF 释放。此外，DEX 处理后 PKCα 的膜易位增强。此外，我们发现 DEX 刺激 GDNF 释放可挽救神经元免受 OGD 诱导的神经毒性；该作用被 GDNF 抗体部分阻断。因此，通过α2A 肾上腺素受体，DEX 可能激活星形胶质细胞，促进 GDNF 释放以保护中风后的神经元，这种信号可能依赖于 PKCα 和 CREB 的激活。
