Molecular mechanism of cerebral ischemia through Jak-Stat signaling

前言：脑缺血诱导了许多生长因子和细胞因子的表达，这些生长因子和细胞因子可以保护神经元免受缺血性脑损伤。例如，睫状神经营养因子（CNTF）、表皮生长因子（EGF）和白细胞介素-6（IL-6）已显示促进Stat 3活化。这些生长因子和细胞因子可以激活Janus蛋白酪氨酸激酶（Jaks）/信号转导和转录激活因子（Stat）途径。最近，我们报道了Stat 3在小鼠脑缺血后被激活[1]。然而，关于活化的Stat 3在缺血脑中的功能知之甚少。在这里，我们证明了活化的Stat 3的表达增加，促进细胞死亡，在培养astrocyres.Methods和结果：星形胶质细胞从新生大鼠前脑培养。如前所述构建表达Stat 3野生型（St3.Wt）、Stat 3显性阴性型（St3.DN）和LacZ的重组腺病毒[2]。星形细胞暴露于 ...更多信息 表达Stat3.Wt、Stat3.DN或LacZ的腺病毒载体（感染复数10）孵育2小时，并与无病毒的新鲜培养基孵育长达72小时。3天后，与对照（LacZ）相比，接种表达St3.wt和St3.DN的病毒载体显著诱导了Stat 3蛋白。Western blot结果显示，Ad.St3.wt能显著诱导p-Stat 3（Tyr-705）的表达，而Ad.St3.DN和Ad.LacZ则不能。这些结果表明，Ad.St3.Wt和Ad.St3.DN都能诱导培养的星形胶质细胞中的Stat 3蛋白，并且只有Ad.St3.Wt能在Tyr-705位点磷酸化Stat 3并激活Stat 3。乳酸脱氢酶（LDH）测定显示，St3.wt过表达促进细胞死亡，而St3.DN和LacZ过表达则无此作用。结论：Stat 3过表达促进了星形胶质细胞的死亡，Caspase-3活性的激活可能参与了这一细胞死亡机制。这些数据揭示了Stat 3的激活在缺血性细胞死亡的机制中起着至关重要的作用。参考文献：[1]Wen et al. ; Neurosci Lett，303：153-156，（2001）[2]Nakajima et al. ; EMBO J，15：3651-58（1996）Less

Introduction :Cerebral ischemia induces the expression of a number of growth factors and cytokines that can protect neurons against ischemic brain injury. For example, ciliary neurotrophic factor (CNTF), epidermal growth factor (EGF) and interleukin-6 (IL-6) have been shown to promote Stat3 activation. These growth factors and cytokines can activate Janus protein tyrosine kinases (Jaks)/signal transducers and activators of transcription (Stat) pathways. Recently, we reported that Stat3 was activated following cerebral ischemia in mouse [1]. However, little is known about the function of activated Stat3 in the ischemic brain. Here we demonstrate the increased expression of activated Stat3 promotes cell death in cultured astrocyres.Methods & Results :Astrocytes from the forebrains of newborn rats were cultured. Recombinant adenovirus expressing Stat3 wild type (St3.Wt), Stat3 dominant negative type (St3.DN) and LacZ were constructed as described previously [2]. Astocytes were exposed to … More adenovirus vector expressing Stat3.Wt, Stat3.DN or LacZ (multiplicity of infection 10) for 2h and incubated with a virus free fresh medium up to 72h. Three days later, inoculation with the virus vectors expressing St3.wt and St3.DN remarkably induced Stat3 protein compared with the control (LacZ). Western blots also revealed that Ad.St3.wt remarkably induced p-Stat3(Tyr-705) while Ad.St3.DN and Ad.LacZ did not. These results demonstrated that both Ad.St3.Wt and Ad.St3.DN induced Stat3 protein in cultured astrocytes and that only Ad.St3.Wt could phosphorylate Stat3 at Tyr-705 site and activate Stat3. LDH assay revealed that overexpression of St3.wt promoted cell death while overexpression of St3.DN and LacZ did not. In addition, caspase-3 like activity of the St3.Wt treated group was significantly increased than that of the St3.DN group at 2d after virus inoculation.Conclusion :We have shown that over-expression of Stat3 promotes cell death in cultured astrocytes, and activation of caspase-3 activity may be involved in this cell death mechanism. These data have revealed that activation of Stat3 can play a crucial role in the mechanism of ischemic cell death.References :[1]Wen et al. ; Neurosci Lett, 303:153-156, (2001)[2]Nakajima et al. ; EMBO J, 15:3651-58 (1996) Less