BACKGROUND: The thioredoxin system maintains redox balance through the action of thioredoxin and thioredoxin reductase. Thioredoxin regulates the activity of various substrates, including those that function to counteract cellular oxidative stress. These include the peroxiredoxins, methionine sulfoxide reductase A and specific transcription factors. Of particular relevance is Redox Factor-1, which in turn activates other redox-regulated transcription factors.
METHODS: Experimentally defined transcription factor binding sites in the human thioredoxin and thioredoxin reductase gene promoters together with promoters of the major thioredoxin system substrates involved in regulating cellular redox status are discussed. An in silico approach was used to identify potential putative binding sites for these transcription factors in all of these promoters.
CONCLUSIONS: Our analysis reveals that many redox gene promoters contain the same transcription factor binding sites. Several of these transcription factors are in turn redox regulated. The ARE is present in several of these promoters and is bound by Nrf2 during various oxidative stress stimuli to upregulate gene expression. Other transcription factors also bind to these promoters during the same oxidative stress stimuli, with this redundancy supporting the importance of the antioxidant response. Putative transcription factor sites were identified in silico, which in combination with specific regulatory knowledge for that gene promoter may inform future experiments.
CONCLUSIONS: Redox proteins are involved in many cellular signalling pathways and aberrant expression can lead to disease or other pathological conditions. Therefore understanding how their expression is regulated is relevant for developing therapeutic agents that target these pathways.

Apelin-13 plays an important role in the migration and proliferation of vascular smooth muscle cells (VSMCs); however, the underlying mechanisms are still unclear. Egr-1 is a nuclear transcription factor, which is considered to be the critical initiating factor of the processes of VSMC proliferation and migration. Egr-1 is known to regulate the expression of osteopontin (OPN), which is a marker of the phenotypic modulation that is a necessary condition of VSMC proliferation and migration. We hypothesized that the role of Apelin-13 is mediated via upregulation of Egr-1. To test this hypothesis, we analyzed the effects of Apelin-13 treatment on Egr-1 mRNA and protein expression in A10 rat aortic VSMCs by RT-PCR and Western blotting, respectively. Results showed that, Apelin-13 upregulated the expression of Egr-1. Furthermore, treatment with the extracellular-regulated protein kinase (ERK) inhibitor, PD98059, inhibited the upregulation of Egr-1 by Apelin-13. In addition, this upregulation was inhibited by treatment of VSMCs with the Egr-1 specific deoxyribozyme ED5 (DNAenzyme/10-23 DRz). Furthermore, ED5 treatment was found to significantly inhibit Apelin-13-induced migration and proliferation of VSMCs using transwell and MTT assays, respectively. The evaluation of OPN mRNA and protein expression levels by RT-PCR and Western blot analyses revealed that ED5 treatment also inhibited Apelin-13-induced OPN upregulation. The results of this study indicated that Apelin-13 upregulates Egr-1 via ERK. Furthermore, Apelin-13 induced the proliferation and migration of VSMCs as well as the upregulation of OPN via the upregulation of Egr-1. These results will provide an important theoretical and experimental basis for the control of inappropriate remodeling of vessel walls, and will hopefully lead to the prevention and treatment of vascular remodeling diseases.