Bioluminescence imaging of Smad signaling in living mice shows correlation with excitotoxic neurodegeneration
Bioluminescence imaging of Smad signaling in living mice shows correlation with excitotoxic neurodegeneration
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DOI：
10.1073/pnas.0605077103
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发表时间：
2006-11-28
影响因子：
11.1
通讯作者：
Wyss-Coray, Tony
中科院分区：
文献类型：
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作者：
Luo, Jian;Lin, Amy H.;Wyss-Coray, Tony
转化生长因子-β信号通路是损伤和免疫反应的关键组织者，最近的研究表明，它在中枢神经系统的功能和维持中发挥着关键作用。转化生长因子-β受体的激活导致Smad蛋白的磷酸化，Smad蛋白随后被转移到细胞核，通过与Smad结合元件(SBE)调节基因转录。使用SBE-荧光素酶报告小鼠，我们最近发现，在小鼠的任何主要器官中，大脑具有最高的Smad基线活性，现在我们证明了这个信号主要定位于海马区的锥体神经元。在体红藻氨酸(KA)兴奋性刺激引起海马CA3区神经元荧光素酶活性和磷酸化Smad2(Smad2P)的增加，Smad2P的核移位与荧光素酶活性显著相关。虽然这种激活在KA注射后24小时在神经元中最为明显，但在3天和5天时，星形胶质细胞和小胶质细胞中Smad2P免疫反应逐渐增强，这与反应性胶质增生相一致。活体小鼠颅骨上的生物发光在伤后12-72h达到高峰，并与损伤后5d小胶质细胞的激活程度和神经变性的病理标志相关。谷氨酸受体拮抗剂MK-801的治疗大大降低了生物发光和病理学。这些结果表明，Smad2信号是神经元激活和中枢神经系统损伤的敏感标志物，可用于监测KA诱导的神经元变性。这种小鼠模型和相关的小鼠模型可能为研究神经退行性变的机制和治疗提供有价值的工具。
The TGF-beta signaling pathway is a key organizer of injury and immune responses, and recent studies suggest it fulfills critical roles in CNS function and maintenance. TGF-beta receptor activation results in phosphorylation of Smad proteins, which subsequently translocate to the nucleus to regulate gene transcription by binding to Smad binding elements (SBE). Using SBE-luciferase reporter mice, we recently discovered that the brain has the highest Smad baseline activity of any major organ in the mouse, and we now demonstrate that this signal is primarily localized to pyramidal neurons of the hippocampus. In vivo excitatory stimulation with kainic acid (KA) resulted in an increase in luciferase activity and phosphorylated Smad2 (Smad2P), and nuclear translocation of Smad2P in hippocampal CA3 neurons correlated significantly with luciferase activity. Although this activation was most prominent at 24 h after KA administration in neurons, Smad2P immunoreactivity gradually increased in astrocytes and microglial cells at 3 and 5 days, consistent with reactive gliosis. Bioluminescence measured over the skull in living mice peaked at 12-72 h and correlated with the extent of microglial activation and pathological markers of neurodegeneration 5 days after injury. Treatment with the glutamate receptor antagonist MK-801 strongly reduced bioluminescence and pathology. These results show that Smad2 signaling is a sensitive marker of neuronal activation and CNS injury that can be used to monitor KA-induced neuronal degeneration. This and related mouse models may provide valuable tools to study mechanisms and treatments for neurodegeneration.