Fig. 1.

ROS is required for cycling hypoxia-mediated HIF-1α and NF-κB activation. The levels of nuclear HIF-1α and p65 (a), HIF-1 dependent transactivation of luciferase activity (b), NF-κB-dependent transactivation of luciferase activity (c), and intracellular ROS (d) in U251and U87 glioblastoma cells exposed to normoxia (Nor), uninterrupted hypoxia (NiH), or cycling hypoxia (CyH) (<1% O₂) with or without Tempol. TATA-binding protein (TBP) was used to normalize protein loading for nuclear extracts. Error bars denote the standard deviation within triplicate experiments. **P < 0.01, ***P < 0.001 compared to normoxia. ^#P < 0.05, ^###P < 0.001 compared to vehicle treatment