College of Oriental Medicine, Kyung Hee University, Seoul, South Korea Yonsei University School of Medicine, Seoul, South Korea.
J Pineal Res. 2011 Aug;51(1):87-93. doi: 10.1111/j.1600-079X.2011.00865.x. Epub 2011 Mar 11.
Sphingosine kinase 1 (SPHK1) is a newly discovered modulator of hypoxia inducible factor 1α (HIF-1α) with various biological activities such as cell growth, survival, invasion, angiogenesis, and carcinogenesis. Thus, in the present study, the biological mechanisms of melatonin were elucidated in association with SPHK1 pathway in PC-3 prostate cancer cells under hypoxia. Melatonin inhibited the stability of HIF-1α in a time- and concentration- dependent manners. Also, melatonin decreased SPHK1 activity in PC-3 cells during hypoxia. Furthermore, melatonin suppressed AKT/glycogen synthase kinase-3β (GSK-3β) signaling pathway, which stabilizes HIF-1α via inhibition of von Hippel-Lindau tumor suppressor protein. Consistently, siRNA-SPHK1 and sphingosine kinase inhibitor (SKI) effectively blocked the expression of HIF-1α, phospho-AKT and vascular endothelial growth factor (VEGF) production in PC-3 cells under hypoxia, suggesting the role of SPHK1 in melatonin-inhibited HIF-1α accumulation. Moreover, reactive oxygen species (ROS) scavenger N-acteylcysteine enhanced melatonin-inhibited HIF-1α expression and SPHK1 activity. Overall, our findings suggest that melatonin suppresses HIF-1α accumulation via inhibition of SPHK1 pathway and ROS generation in PC-3 cells under hypoxia.
鞘氨醇激酶 1（SPHK1）是一种新发现的缺氧诱导因子 1α（HIF-1α）调节剂，具有多种生物学活性，如细胞生长、存活、侵袭、血管生成和致癌作用。因此，在本研究中，探讨了褪黑素在缺氧条件下通过 SPHK1 途径对 PC-3 前列腺癌细胞的生物学机制。褪黑素呈时间和浓度依赖性抑制 HIF-1α的稳定性。此外，褪黑素在缺氧时降低 PC-3 细胞中的 SPHK1 活性。此外，褪黑素抑制 AKT/糖原合酶激酶-3β（GSK-3β）信号通路，通过抑制 von Hippel-Lindau 肿瘤抑制蛋白稳定 HIF-1α。一致地，siRNA-SPHK1 和鞘氨醇激酶抑制剂（SKI）有效地阻断了缺氧条件下 PC-3 细胞中 HIF-1α、磷酸化 AKT 和血管内皮生长因子（VEGF）的表达，表明 SPHK1 在褪黑素抑制 HIF-1α积累中的作用。此外，活性氧（ROS）清除剂 N-乙酰半胱氨酸增强了褪黑素抑制的 HIF-1α表达和 SPHK1 活性。总之，我们的研究结果表明，褪黑素通过抑制缺氧条件下 PC-3 细胞中 SPHK1 途径和 ROS 的产生来抑制 HIF-1α的积累。
