Abstract
The NADPH oxidase isoform NOX4 produces mainly hydrogen peroxide (H 2 O 2 ). The transcription factor NRF2 is a key mediator of cellular adaptation to redox stress. Regulation of NOX4 and formation of H 2 O 2 might be directly linked to NO release. NOX4 is the major endothelial NOX isoform and considered to be constitutively active. Regulation of NOX4 on transcriptional level by NRF2 might be directly linked to NO release and endothelial function. Endothelial cells (HUVEC) were constantly exposed to high laminar shear stress (24h, 30dyn/cm 2 ). This stimulates NO formation and leads to elongation of the cells in the direction of the flow. Previously, we could show that NOX4 is the major endothelial NOX isoform and downregulated by shear stress. Here we show that shear stress induces antioxidative response via upregulation of NRF2 which affects NOX4 expression. We transduced HUVEC with lentiviral particles containing short hairpin RNA (sh) against NRF2 and NOX4. Lentiviral downregulation of NOX4 using shNOX4 inhibited the shear stress-dependent elongation of cell shape in response to flow. Application of shear stress caused downregulation of NOX4 and upregulation of NRF2 and its target genes NQO-1 and HO-1. Attenuation of NRF2 by shNRF2 inhibited shear stress-dependent induction of NRF2 and its target genes. In addition, shNRF2 enhanced the shear stress-dependent downregulation of NOX4. Finally, we could show that downregulation of NOX4 is involved in the upregulation of eNOS and expression of NRF2 in response to flow. Nox4 overexpression had no effect on these processes. In conclusion, our data suggest a link between NOX4, NRF2-mediated antioxidative response and endothelial function.
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