Jang Jung-Hee, Surh Young-Joon
Laboratory of Biochemistry and Molecular Toxicology, College of Pharmacy, Seoul National University, Seoul, South Korea.
Redox Rep. 2004;9(6):343-8. doi: 10.1179/135100004225006858.
Bcl-X(L), a mitochondrial membrane protein, blocks apoptosis induced by a wide array of death signals. In spite of extensive research, the molecular milieu that characterizes the anti-apoptotic function of Bcl-X(L) is complex and not fully clarified. In the present work, we have investigated the role of Bcl-X(L) in protecting against oxidative death induced by H(2)O(2) in cultured rat pheochromocytoma (PC12) cells. PC12 cells exposed to H(2)O(2) underwent apoptotic cell death as determined by internucleosomal DNA fragmentation and an increased pro-apoptotic Bax to anti-apoptotic Bcl-X(L) ratio. Moreover, stable transfection with the bcl-X(L) gene rescued PC12 cells from apoptotic death caused by H(2)O(2). PC12 cells overexpressing bcl-X(L) exhibited relatively high constitutive transcriptional as well as DNA binding activities of NF-kappaB, compared with the vector-transfected control cells. Addition of NF-kappaB inhibitors, such as parthenolide and N-tosyl-L-phenylalanine chloromethyl ketone, to the media aggravated H(2)O(2)-induced oxidative cell death. PC12 cells transfected with bcl-X(L) exhibited higher levels of the heme oxygenase-1, which may confer these cells protection against oxidative stress. These results suggest that the redox-sensitive transcription factor NF-kappaB may play a role in bcl-X(L)-mediated protection against oxidative cell death.
Bcl-X(L)是一种线粒体膜蛋白，可阻断多种死亡信号诱导的细胞凋亡。尽管已进行了广泛研究，但表征Bcl-X(L)抗凋亡功能的分子环境复杂且尚未完全阐明。在本研究中，我们研究了Bcl-X(L)在保护培养的大鼠嗜铬细胞瘤（PC12）细胞免受H₂O₂诱导的氧化死亡中的作用。通过核小体间DNA片段化以及促凋亡的Bax与抗凋亡的Bcl-X(L)比例增加来确定，暴露于H₂O₂的PC12细胞发生了凋亡性细胞死亡。此外，用bcl-X(L)基因进行稳定转染可使PC12细胞免于H₂O₂引起的凋亡性死亡。与载体转染的对照细胞相比，过表达bcl-X(L)的PC12细胞表现出相对较高的组成型转录以及NF-κB的DNA结合活性。向培养基中添加NF-κB抑制剂，如小白菊内酯和N-对甲苯磺酰-L-苯丙氨酸氯甲基酮，会加重H₂O₂诱导的氧化细胞死亡。用bcl-X(L)转染的PC12细胞表现出较高水平的血红素加氧酶-1，这可能赋予这些细胞抗氧化应激的保护作用。这些结果表明，对氧化还原敏感的转录因子NF-κB可能在bcl-X(L)介导的抗氧化细胞死亡保护中发挥作用。
