Abstract 11392: The Hypoxia-Inducible Factor Pathway in Varicose Veins
Introduction Many structural and biochemical changes known to be regulated by hypoxia and mechanical stretch have been reported in varicose vein (VV) wall. Hypoxia-inducible factors (HIFs) are nuclear transcriptional factors known to be regulated by hypoxia and mechanical stretch, and they control the expression of genes mediating oxygen homeostasis. This study aimed to assess the expression of HIF-α, HIF target genes, and HIF regulatory enzymes in VV and non-varicose veins (NVV), and their regulation by hypoxia.
Methods The mRNA and protein expression of HIF-1α, HIF-2α, HIF target genes, and HIF regulatory enzymes in surgically retrieved VV and NVV was analyzed using Q-PCR, Western blot and immunohistochemistry. VV and NVV organ cultures (n=6) were also prepared and exposed to normoxia, hypoxia (1% oxygen), or the hypoxia mimetic dimethyloxallyl glycine (DMOG). HIF-1α, HIF-2α, and HIF target genes expression was measured.
Results HIF-1α and HIF-2α mRNA and protein expression was increased in VV compared to NVV. Similarly, the mRNA expression of all HIF target genes (CA9, GLUT-1, VEGF, BNIP-3, PHD-2 and PHD-3 and ENO-1) measured was also up-regulated in VV compared to NVV. Using immunohistochemistry, HIF-1α expression was found localized to endothelial cells, whereas HIF-2α and target genes (CA9 and PHD-2) were expressed by smooth muscle and endothelial cells. The expression of prolyl-hydroxylase domain (PHD)-2, and PHD-3, but not PHD-1 and factor inhibiting HIF-1 was increased in VV compared to NVV. Increased HIF-1α and HIF-2α protein expression was observed in VV and NVV exposed to hypoxia or DMOG compared to normoxia. Significant increases of HIF target genes (CA9, BNIP-3, GLUT-1, PHD-2 and PHD-3) mRNA expression were also observed in VV and NVV in hypoxia or DMOG compared to normoxia. The up-regulation of HIF target genes in VV and NVV by hypoxia or DMOG was also reflected at protein level.
Conclusions VV demonstrate increased activation of the HIF pathway compared to NVV. Exposure of VV and NVV to hypoxia is associated with increased HIF pathway activation. The data suggest that the HIF pathway may be an important regulator of biochemical and structural changes in the VV wall, and hence a potential therapeutic target.
- © 2011 by American Heart Association, Inc.