Arterial flow reduces oxidative stress via an antioxidant response element and Oct-1 binding site within the NADPH oxidase 4 promoter in endothelial cells

• DOI: 10.1007/s00395-011-0170-3
• Publication Date: 2011-03-11T13:36:57Z
• Authors: Claudia Goettsch; Winfried Goettsch; Melanie Brux; Claudia Haschke; Coy Brunssen; Gregor Muller; Stefan R. Bornstein; Nicole Duerrschmidt; Andreas H. Wagner; Henning Morawietz
• Keywords: 0303 health sciences; Binding Sites; NF-E2-Related Factor 2; Endothelial Cells; NADPH Oxidases; Response Elements; Antioxidants; Oxidative Stress; 03 medical and health sciences; NADPH Oxidase 4; Regional Blood Flow; Humans; Stress, Mechanical; Promoter Regions, Genetic; Reactive Oxygen Species; Cells, Cultured; Octamer Transcription Factor-1

The main sources of oxidative stress in the vessel wall are nicotine adenine dinucleotide phosphate (NADPH) oxidase (Nox) complexes. The endothelium mainly expresses the Nox4-containing complex; however, the mechanism by which shear stress in endothelial cells regulates Nox4 is not well understood. This study demonstrates that long-term application of arterial laminar shear stress using a cone-and-plate viscometer reduces endothelial superoxide anion formation and Nox4 expression. In primary human endothelial cells, we identified a 47 bp 5'-untranslated region of Nox4 mRNA by 5'-rapid amplification of cDNA ends (5'-RACE) PCR. Cloning and functional analysis of human Nox4 promoter revealed a range between -1,490 and -1,310 bp responsible for flow-dependent downregulation. Mutation of an overlapping antioxidative response element (ARE)-like and Oct-1 binding site at -1,376 bp eliminated shear stress-dependent Nox4 downregulation. Consistent with these observations, electrophoretic mobility shift assays (EMSA) demonstrated an enhanced shear stress-dependent binding of Nox4 oligonucleotide containing the ARE-like/Oct-1 binding site, which could be inhibited by specific antibodies against the transcription factors nuclear factor erythroid 2-related factor 2 (Nrf2) and octamer transcription factor 1 (Oct-1). Furthermore, shear stress caused the translocation of Nrf2 and Oct-1 from the cytoplasm to the nucleus. Knockdown of Nrf2 by short hairpin RNA (shRNA) increased Nox4 expression twofold, indicating a direct cross-talk between Nrf2 and Nox4. In conclusion, an ARE-like/Oct-1 binding site was noticed to be essential for shear stress-dependent downregulation of Nox4. This novel mechanism may be involved in the flow-dependent downregulation of endothelial superoxide anion formation.