Institut für Physiologie, Universität Duisburg-Essen, Germany.
Free Radic Res. 2012 Jun;46(6):705-17. doi: 10.3109/10715762.2012.669041. Epub 2012 Apr 3.
The function and survival of eukaryotic cells depends on a constant and sufficient oxygen supply. Cells recognize and respond to hypoxia by accumulation of the transcription factor hypoxia-inducible factor 1 (HIF-1), composed of an oxygen-sensitive HIF-1α and a constitutive HIF-1β subunit. Besides physiology, HIF-1 induction is involved in major pathological processes such as cardiovascular disease, inflammation and cancer, which are associated with the formation of reactive oxygen species (ROS). ROS have been reported to affect HIF-1 activity but the role for ROS in regulating HIF-1 has not been definitely settled. In order to shed light on the redox-regulation of HIF-1 by ROS, we studied the impact of exogenous ROS treatment (H(2)O(2)) on HIF-1α and HIF-1 regulatory protein prolyl hydroxylase 2 (PHD2) in the human osteosarcoma cell line U2OS. At early reaction periods, H(2)O(2) induced HIF-1α but at prolonged observation phases the opposite occurred. Herein, modulation of PHD activity appeared to be the key element, because knockdown and inhibition of the PHD2 prevented reduction of HIF-1α. However, H(2)O(2) treatment constantly suppressed HIF-1 transactivation at all time-points. Our data indicate a dual redox regulation of HIF-1α protein amount with a constant suppression of HIF-1 target gene expression by ROS.
真核细胞的功能和存活依赖于恒定且充足的氧气供应。细胞通过积累转录因子缺氧诱导因子 1（HIF-1）来识别和响应缺氧，HIF-1 由对氧气敏感的 HIF-1α和组成型 HIF-1β亚基组成。除了生理学，HIF-1 的诱导还涉及主要的病理过程，如心血管疾病、炎症和癌症，这些过程与活性氧（ROS）的形成有关。已经有报道称 ROS 会影响 HIF-1 的活性，但 ROS 在调节 HIF-1 中的作用尚未得到明确解决。为了阐明 ROS 对 HIF-1 的氧化还原调节作用，我们研究了外源性 ROS 处理（H2O2）对人骨肉瘤细胞系 U2OS 中 HIF-1α 和 HIF-1 调节蛋白脯氨酰羟化酶 2（PHD2）的影响。在早期反应阶段，H2O2 诱导了 HIF-1α，但在延长的观察阶段则相反。在此，PHD 活性的调节似乎是关键因素，因为 PHD2 的敲低和抑制阻止了 HIF-1α的减少。然而，H2O2 处理始终在所有时间点抑制 HIF-1 转录激活。我们的数据表明，ROS 对 HIF-1α 蛋白水平的双重氧化还原调节，导致 HIF-1 靶基因表达的持续抑制。
