Department of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea.
Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul 137-701, Republic of Korea.
Int J Oncol. 2014 Mar;44(3):761-8. doi: 10.3892/ijo.2013.2227. Epub 2013 Dec 23.
A recent study reported that p53 can induce HO-1 by directly binding to the putative p53 responsive element in the HO-1 promoter. In this study, we report that nutlin-3, a small molecule antagonist of HDM2, induces the transcription of HO-1 in a transcription-independent manner of p53. Nutlin-3 induced HO-1 expression at the level of transcription in human cancer cells such as U2OS and RKO cells. This induction of HO-1 did not occur in SAOS cells in which p53 was mutated and was prevented by knocking down the p53 protein using p53 siRNA transfection, but not by PFT-α, an inhibitor of the transcriptional activity of p53. Accompanying HO-1 expression, nutlin-3 stimulated the accumulation of ROS and the phosphorylation of MAPKs such as JNK, p38 MAPK and ERK1/2. Nutlin-3-induced HO-1 expression was suppressed by TEMPO, a ROS scavenger, and chemical inhibitors of JNK and p38 MAPK but not ERK1/2. In addition, nutlin‑3-induced phosphorylation of JNK but not p38 MAPK was inhibited by TEMPO. Notably, the levels of nutlin-3-induced ROS were correlated with the mitochondrial translocation of p53 and this induction was prevented by PFT-μ, an inhibitor of the mitochondrial translocation of p53. Consistent with the effect of the ROS scavenger and MAPK inhibitors, PFT-μ reduced HO-1 expression and the phosphorylation of JNK induced by nutlin-3. In the experiments of analyzing cell death, the knockdown of HO-1 augmented nutlin-3-induced apoptosis. Collectively, these results suggest that nutlin-3 induces HO-1 expression via the activation of both JNK which is dependent on ROS generated by p53 translocated to the mitochondria and p38 MAPK which appears to be stimulated by a ROS-independent mechanism, and this HO-1 induction may inhibit nutlin-3-induced apoptosis, constituting a negative feedback loop of p53-induced apoptosis.
最近的一项研究报道称，p53 可以通过直接结合 HO-1 启动子中的推定 p53 反应元件来诱导 HO-1。在这项研究中，我们报告说，小分子 HDM2 拮抗剂 nutlin-3 以不依赖 p53 的转录方式诱导 HO-1 的转录。Nutlin-3 在人类癌细胞（如 U2OS 和 RKO 细胞）中诱导 HO-1 的转录水平表达。这种 HO-1 的诱导不会发生在 p53 发生突变的 SAOS 细胞中，并且可以通过使用 p53 siRNA 转染敲低 p53 蛋白来阻止，但不能通过 PFT-α（p53 转录活性的抑制剂）来阻止。伴随着 HO-1 的表达，nutlin-3 刺激 ROS 的积累和 MAPKs（如 JNK、p38 MAPK 和 ERK1/2）的磷酸化。ROS 清除剂 TEMPO、JNK 和 p38 MAPK 的化学抑制剂但不是 ERK1/2 可抑制 nutlin-3 诱导的 HO-1 表达。此外，nutlin-3 诱导的 JNK 磷酸化但不是 p38 MAPK 磷酸化被 TEMPO 抑制。值得注意的是，nutlin-3 诱导的 ROS 水平与 p53 的线粒体易位相关，并且这种诱导被 p53 线粒体易位抑制剂 PFT-μ 所阻止。与 ROS 清除剂和 MAPK 抑制剂的作用一致，PFT-μ 降低了 nutlin-3 诱导的 HO-1 表达和 JNK 的磷酸化。在分析细胞死亡的实验中，HO-1 的敲低增强了 nutlin-3 诱导的细胞凋亡。总之，这些结果表明，nutlin-3 通过激活依赖于 p53 易位到线粒体产生的 ROS 的 JNK 和似乎由 ROS 非依赖性机制刺激的 p38 MAPK 诱导 HO-1 表达，并且这种 HO-1 诱导可能抑制 nutlin-3 诱导的细胞凋亡，构成 p53 诱导的细胞凋亡的负反馈回路。
