Xiang H, Kinoshita Y, Knudson C M, Korsmeyer S J, Schwartzkroin P A, Morrison R S
Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington 98195-6470, USA.
J Neurosci. 1998 Feb 15;18(4):1363-73. doi: 10.1523/JNEUROSCI.18-04-01363.1998.
The tumor suppressor gene p53 has been implicated in the loss of neuronal viability, but the signaling events associated with p53-mediated cell death in cortical and hippocampal neurons are not understood. Previous work has shown that adenovirus-mediated delivery of the p53 gene causes cortical and hippocampal neuronal cell death with some features typical of apoptosis. In the present study we determined whether p53-initiated changes in neuronal viability were dependent on members of the Bcl-2 family of cell death regulators. Primary cultures of cortical neurons were derived from animals containing Bax (+/+ and +/-) or those deficient in Bax (-/-). Cell damage was assessed by direct cell counting and by measurements of MTT activity. Neurons containing at least one copy of the Bax gene were damaged severely by exposure to excitotoxins or by the induction of DNA damage. In contrast, Bax-deficient neurons (-/-) exhibited significant protection from both types of injury. Bax protein expression was elevated significantly by glutamate exposure, but not by camptothecin-induced DNA damage in wild-type neurons. The glutamate-induced increase in Bax protein was dependent on the presence of the p53 gene. However, increased p53 expression, using adenovirus-mediated transduction, was not sufficient by itself to elevate Bax protein levels. These results demonstrate that Bax is required for neuronal cell death in response to some forms of cytotoxic injury and further support the key role for p53 activation in response to excitotoxic and genotoxic injury.
肿瘤抑制基因p53与神经元活力丧失有关，但与p53介导的皮质和海马神经元细胞死亡相关的信号事件尚不清楚。先前的研究表明，腺病毒介导的p53基因传递会导致皮质和海马神经元细胞死亡，并具有一些典型的凋亡特征。在本研究中，我们确定了p53引发的神经元活力变化是否依赖于细胞死亡调节因子Bcl-2家族的成员。皮质神经元的原代培养物来自含有Bax（+/+和+/-）的动物或缺乏Bax（-/-）的动物。通过直接细胞计数和MTT活性测量来评估细胞损伤。含有至少一个Bax基因拷贝的神经元在暴露于兴奋性毒素或诱导DNA损伤时会受到严重损伤。相比之下，缺乏Bax的神经元（-/-）对这两种类型的损伤均表现出显著的保护作用。在野生型神经元中，谷氨酸暴露可显著提高Bax蛋白表达，但喜树碱诱导的DNA损伤则不会。谷氨酸诱导的Bax蛋白增加依赖于p53基因的存在。然而，使用腺病毒介导的转导增加p53表达本身并不足以提高Bax蛋白水平。这些结果表明，Bax是某些形式的细胞毒性损伤后神经元细胞死亡所必需的，并进一步支持了p53激活在应对兴奋性毒性和基因毒性损伤中的关键作用。
