The nuclear receptor NOR-1 modulates redox homeostasis in human vascular smooth muscle cells

Abstract

The nuclear receptor NOR-1 (Neuron-derived Orphan Receptor-1) has recently been involved in vascular remodeling and coronary artery disease, however, to date, only a few NOR-1 target genes have been described. We aimed to identify genes regulated by NOR-1 in human vascular smooth muscle cells (VSMC). Lentiviral overexpression of NOR-1 increases reactive oxygen species (ROS) in human VSMC. In accordance, NOR-1 strongly increased NADPH oxidase NOX1 mRNA and protein levels, while NOR-1 silencing significantly reduced NOX1 expression. Luciferase reporter, site-directed mutagenesis and EMSA studies identified two nerve growth factor-induced clone B (NGFI-B)-response elements (NBREs) in NOX1 promoter as essential elements for NOR-1 responsiveness. NOR-1 and NOX1 were co-expressed by VSMC in human atherosclerotic lesions, and NOX1 knockdown counteracted the increased ROS production and cell migration induced by NOR-1 overexpression. NOR-1 also modulated the expression of other enzymes involved in cellular redox status, in particular, upregulated superoxide dismutase-1 (SOD1) and SOD3 while downregulated SOD2 and NOX4. NOR-1 induced SOD1 and SOD3 transcriptional activity and participated in the modulation of SOD3 by inflammatory stimuli. By contrast, NOR-1 impaired SOD2 transcription antagonizing NFκB signaling. These results indicate that NOR-1 induces NOX1 in human VSMC and participates in the complex gene networks regulating oxidative stress and redox homeostasis in the vasculature.