Division of Hematology and Oncology, Comprehensive Cancer Center, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA.
Cell Death Dis. 2013 Oct 3;4(10):e824. doi: 10.1038/cddis.2013.358.
Piperlongumine (PL), a natural product isolated from the plant species Piper longum L., can selectively induce apoptotic cell death in cancer cells by targeting the stress response to reactive oxygen species (ROS). Here we show that PL induces cell death in the presence of benzyloxycarbonylvalyl-alanyl-aspartic acid (O-methyl)-fluoro-methylketone (zVAD-fmk), a pan-apoptotic inhibitor, and in the presence of necrostatin-1, a necrotic inhibitor. Instead PL-induced cell death can be suppressed by 3-methyladenine, an autophagy inhibitor, and substantially attenuated in cells lacking the autophagy-related 5 (Atg5) gene. We further show that PL enhances autophagy activity without blocking autophagy flux. Application of N-acetyl-cysteine, an antioxidant, markedly reduces PL-induced autophagy and cell death, suggesting an essential role for intracellular ROS in PL-induced autophagy. Furthermore, PL stimulates the activation of p38 protein kinase through ROS-induced stress response and p38 signaling is necessary for the action of PL as SB203580, a p38 inhibitor, or dominant-negative p38 can effectively reduce PL-mediated autophagy. Thus, we have characterized a new mechanism for PL-induced cell death through the ROS-p38 pathway. Our findings support the therapeutic potential of PL by triggering autophagic cell death.
胡椒碱（PL）是从植物胡椒属植物中分离出来的天然产物，通过靶向活性氧（ROS）应激反应，可选择性诱导癌细胞凋亡。在这里，我们表明，PL 在苯甲氧基羰基缬氨酰 - 丙氨酰 - 天冬氨酸（O-甲基）- 氟甲基酮（zVAD-fmk）（一种通用的凋亡抑制剂）和在坏死抑制剂 Necrostatin-1 的存在下诱导细胞死亡。相反，PL 诱导的细胞死亡可被自噬抑制剂 3-甲基腺嘌呤抑制，并在缺乏自噬相关 5 基因（Atg5）的细胞中显著减弱。我们进一步表明，PL 增强了自噬活性，而不会阻断自噬通量。抗氧化剂 N-乙酰半胱氨酸的应用显著降低了 PL 诱导的自噬和细胞死亡，表明细胞内 ROS 在 PL 诱导的自噬中起重要作用。此外，PL 通过 ROS 诱导的应激反应刺激 p38 蛋白激酶的激活，并且 p38 信号通路是 PL 作用所必需的，因为 p38 抑制剂 SB203580 或显性负性 p38 可有效减少 PL 介导的自噬。因此，我们通过 ROS-p38 通路描述了 PL 诱导细胞死亡的新机制。我们的研究结果支持了 PL 通过触发自噬细胞死亡的治疗潜力。
