Increased Oxidative Stress and Hypoxia Inducible Factor-1 Expression during Arteriovenous Fistula Maturation

BACKGROUND: The poor clinical results that are frequently reported for arteriovenous fistulae (AVF) for hemodialysis are typically due to failure of AVF maturation. We hypothesized that early AVF maturation is associated with generation of reactive oxygen species and activation of the HIF-1 pathway, potentially promoting neointimal hyperplasia. We tested this hypothesis using a previously reported mouse AVF model that recapitulates human AVF maturation. METHODS: Aortocaval fistulae were created in C57Bl/6 mice, and compared to sham-operated mice. AVFs or inferior vena cavas were analysed using a microarray, Amplex Red for extracellular H2O2, qPCR, immunohistochemistry, and immunoblotting for HIF-1α, and immunofluorescence for NOX-2, nitrotyrosine, HO-1 and VEGF-A. RESULTS: Oxidative stress was higher in AVF compared to control veins, with more H2O2 (p=0.007) and enhanced nitrotyrosine immunostaining (p=0.005). Immunohistochemistry and immunoblot showed increased HIF-1α immunoreactivity in the AVF endothelium; HIF-1 targets NOX-2, HO-1 and VEGF-A were overexpressed in the AVF (p<0.01). AVF expressed increased numbers of HIF-1α (p<0.0001) and HO-1 (p<0.0001) mRNA transcripts. CONCLUSIONS: Oxidative stress increases in mouse AVF during early maturation, with increased expression of HIF-1α and its target genes NOX-2, HO-1 and VEGF-A. These results suggest that clinical strategies to improve AVF maturation could target the HIF-1 pathway.