Chaudhari Atul A, Seol Jae-Won, Kim Shang-Jin, Lee You-Jin, Kang Hyung-Sub, Kim In-Shik, Kim Nam-Soo, Park Sang-Youel
Center for Healthcare Technology Development, Bio-Safty Research Institute College of Veterinary Medicine, Chonbuk National University, Jeonbuk 561-756, South Korea.
Oncol Rep. 2007 Jul;18(1):71-6.
TRAIL is a TNF family member that engages apoptosis via recruitment and rapid activation of caspase-8. Oxygen-free radicals, more generally known as reactive oxygen species (ROS) are well recognized for playing an important role in the regulation of tumor cell apoptosis. ROS within the cells act as secondary messengers in intracellular signalling cascades therefore function as anti-tumorigenic species. But very little is known about the effect of ROS on TRAIL-induced apoptosis. In this study we investigated the effect of CCCP, a classic uncoupler of oxidative phosphorylation, on TRAIL-induced apoptosis in TRAIL-resistant MCF-7 cells. It was found that pretreatment with CCCP for 6 h and then treatment with TRAIL for additional 3 h markedly enhanced apoptosis by 2-fold as compared with TRAIL alone. The uncoupling effect enhanced TRAIL-induced apoptosis by ROS generation. Moreover, CCCP treatment also reduced mitochondrial transmembrane potential (MTP, Delta Psi m) and induced Bax translocation to the mitochondria of its own account. This sensitization was inhibited with N-acetyl-L-cysteine (NAC) treatment by abrogating the ROS which was generated by the combined treatment of CCCP and TRAIL. Of interest, NAC also inhibited reduction of the Delta Psi m and Bax translocation after CCCP pretreatment which suggest that the generation of ROS may precede the loss in MTP. Thus, we demonstrated that CCCP-induced ROS generation enhanced TRAIL induced apoptosis by regulation of Bax translocation and mitochondrial transmembrane potential. The enhancing effect by CCCP-induced ROS generation was restored after NAC treatment. Therefore, our results suggest that uncoupling the cells by CCCP can overcome the resistance to TRAIL protein and can be a very efficient treatment for the tumor cells especially resistant to TRAIL-induced apoptosis.
肿瘤坏死因子相关凋亡诱导配体（TRAIL）是肿瘤坏死因子（TNF）家族成员，通过募集并快速激活半胱天冬酶 - 8诱导细胞凋亡。氧自由基，更普遍地称为活性氧（ROS），在肿瘤细胞凋亡调控中发挥重要作用已得到广泛认可。细胞内的ROS作为细胞内信号级联反应中的第二信使，因此具有抗肿瘤作用。但关于ROS对TRAIL诱导凋亡的影响知之甚少。在本研究中，我们研究了氧化磷酸化的经典解偶联剂碳酰氰间氯苯腙（CCCP）对TRAIL耐药的MCF - 7细胞中TRAIL诱导凋亡的影响。结果发现，用CCCP预处理6小时，然后再用TRAIL处理3小时，与单独使用TRAIL相比，凋亡明显增强了2倍。解偶联作用通过产生ROS增强了TRAIL诱导的凋亡。此外，CCCP处理还降低了线粒体跨膜电位（MTP，ΔΨm），并自身诱导Bax转位至线粒体。通过消除CCCP和TRAIL联合处理产生的ROS，N - 乙酰 - L - 半胱氨酸（NAC）处理抑制了这种致敏作用。有趣的是，NAC还抑制了CCCP预处理后ΔΨm的降低和Bax转位，这表明ROS的产生可能先于MTP的丧失。因此，我们证明CCCP诱导的ROS产生通过调节Bax转位和线粒体跨膜电位增强了TRAIL诱导的凋亡。NAC处理后，CCCP诱导的ROS产生的增强作用得以恢复。因此，我们的结果表明，CCCP使细胞解偶联可以克服对TRAIL蛋白的耐药性，并且对于尤其对TRAIL诱导凋亡耐药的肿瘤细胞可能是一种非常有效的治疗方法。
