Kemler I, Fontana A
Department of Internal Medicine, University Hospital, Zürich, Switzerland.
Glia. 1999 May;26(3):212-20.
In infectious diseases of the central nervous system astrocytes respond to inflammatory cytokines like tumor necrosis factor alpha (TNFalpha) by activation of the transcription factor NF-kappaB, mediated by the proteolysis of its inhibitors IkappaBalpha and IkappaBbeta. We studied the kinetics of NF-kappaB induction by TNFalpha in primary astrocytes, and in the neuroblastoma cell line Neuro2A, and compared it to fibroblasts. In the latter, NF-kappaB DNA binding activity was induced at 30 min and remained constant up to 4 h. In contrast, in astrocytes and in Neuro2A cells NF-kappaB DNA binding activity followed a biphasic pattern: it was induced after 30 min (early phase), declined after 1 h, and increased again at 2 to 4 h (late phase). The early phase was due to rapid degradation of IkappaBalpha. After 1 h IkappaBalpha was resynthesized to levels exceeding the amounts present in unstimulated cells. This paralleled the low levels of nuclear NF-kappaB binding activity. The decrease was not observed when IkappaBalpha resynthesis was inhibited by cycloheximide. Degradation of both IkappaBalpha and IkappaBbeta contributed to the late phase of induction. However, the second peak occurred also in the absence of IkappaBbeta proteolysis, demonstrating the importance of IkappaBalpha in the formation of the biphasic nuclear translocation of NF-kappaB.
在中枢神经系统的感染性疾病中，星形胶质细胞通过转录因子NF-κB的激活对诸如肿瘤坏死因子α（TNFα）等炎性细胞因子作出反应，这是由其抑制剂IκBα和IκBβ的蛋白水解介导的。我们研究了TNFα在原代星形胶质细胞和成神经细胞瘤细胞系Neuro2A中诱导NF-κB的动力学，并将其与成纤维细胞进行比较。在成纤维细胞中，NF-κB DNA结合活性在30分钟时被诱导，并在长达4小时内保持恒定。相比之下，在星形胶质细胞和Neuro2A细胞中，NF-κB DNA结合活性呈现双相模式：在30分钟后被诱导（早期阶段），在1小时后下降，并在2至4小时再次升高（晚期阶段）。早期阶段是由于IκBα的快速降解。1小时后，IκBα重新合成至超过未刺激细胞中存在的量。这与核NF-κB结合活性的低水平平行。当用放线菌酮抑制IκBα重新合成时未观察到下降。IκBα和IκBβ的降解都促成了诱导的晚期阶段。然而，在没有IκBβ蛋白水解的情况下也出现了第二个峰值，这证明了IκBα在NF-κB双相核转位形成中的重要性。
